/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class Main
{ 
   
  public static void main (String[] args) throws java.lang.Exception
   {
	try{
	     //long a=Long.parseLong(next());
	    // int a=sc.nextInt();
	     Reader sc=new Reader();
	     PrintWriter out=new PrintWriter(System.out);
	     long n=sc.nextInt();
		  long x=sc.nextInt();
		  long t=sc.nextInt();
		  
		  long val=(long)Math.ceil((double)n/(double)x);
		  out.println(val*t);
		      
		      
		      
		    
	out.flush();
	out.close();
	   }     
	catch(Exception e)
		 {}
	}
	//Template
  // static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
   //  static PrintWriter pw = new PrintWriter(System.out);
   //  static StringTokenizer st;
    
   //  static String next()
   //     {
   //          while(st==null || !st.hasMoreElements()) 
   //          {
   //              try
   //              {
   //                 st = new StringTokenizer(br.readLine());
   //              }
   //              catch(IOException e)
   //              {
   //                 e.printStackTrace();
   //              }
   //          }
   //          return st.nextToken();
   //     }
   // static int gcd(int a,int b)
   //  {
   //     if(b==0)
   //     return a;
   //     else
   //     return gcd(b,a%b);
   //  }
   
    static class Reader 
    { 
        final private int BUFFER_SIZE = 1 << 16; 
        private DataInputStream din; 
        private byte[] buffer; 
        private int bufferPointer, bytesRead; 
  
        public Reader() 
        { 
            din = new DataInputStream(System.in); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public Reader(String file_name) throws IOException 
        { 
            din = new DataInputStream(new FileInputStream(file_name)); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public String readLine() throws IOException 
        { 
            byte[] buf = new byte[64]; // line length 
            int cnt = 0, c; 
            while ((c = read()) != -1) 
            { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } 
            return new String(buf, 0, cnt); 
        } 
  
        public int nextInt() throws IOException 
        { 
            int ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do
            { 
                ret = ret * 10 + c - '0'; 
            }  while ((c = read()) >= '0' && c <= '9'); 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public long nextLong() throws IOException 
        { 
            long ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public double nextDouble() throws IOException 
        { 
            double ret = 0, div = 1; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
  
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
  
            if (c == '.') 
            { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        private void fillBuffer() throws IOException 
        { 
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
            if (bytesRead == -1) 
                buffer[0] = -1; 
        } 
  
        private byte read() throws IOException 
        { 
            if (bufferPointer == bytesRead) 
                fillBuffer(); 
            return buffer[bufferPointer++]; 
        } 
  
        public void close() throws IOException 
        { 
            if (din == null) 
                return; 
            din.close(); 
        } 
    } 

} import java.util.*; util.* java import java.lang.*; lang.* java import java.io.*; io.* java public class Main
{ 
   
  public static void main (String[] args) throws java.lang.Exception
   {
	try{
	     //long a=Long.parseLong(next());
	    // int a=sc.nextInt();
	     Reader sc=new Reader();
	     PrintWriter out=new PrintWriter(System.out);
	     long n=sc.nextInt();
		  long x=sc.nextInt();
		  long t=sc.nextInt();
		  
		  long val=(long)Math.ceil((double)n/(double)x);
		  out.println(val*t);
		      
		      
		      
		    
	out.flush();
	out.close();
	   }     
	catch(Exception e)
		 {}
	}
	//Template
  // static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
   //  static PrintWriter pw = new PrintWriter(System.out);
   //  static StringTokenizer st;
    
   //  static String next()
   //     {
   //          while(st==null || !st.hasMoreElements()) 
   //          {
   //              try
   //              {
   //                 st = new StringTokenizer(br.readLine());
   //              }
   //              catch(IOException e)
   //              {
   //                 e.printStackTrace();
   //              }
   //          }
   //          return st.nextToken();
   //     }
   // static int gcd(int a,int b)
   //  {
   //     if(b==0)
   //     return a;
   //     else
   //     return gcd(b,a%b);
   //  }
   
    static class Reader 
    { 
        final private int BUFFER_SIZE = 1 << 16; 
        private DataInputStream din; 
        private byte[] buffer; 
        private int bufferPointer, bytesRead; 
  
        public Reader() 
        { 
            din = new DataInputStream(System.in); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public Reader(String file_name) throws IOException 
        { 
            din = new DataInputStream(new FileInputStream(file_name)); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public String readLine() throws IOException 
        { 
            byte[] buf = new byte[64]; // line length 
            int cnt = 0, c; 
            while ((c = read()) != -1) 
            { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } 
            return new String(buf, 0, cnt); 
        } 
  
        public int nextInt() throws IOException 
        { 
            int ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do
            { 
                ret = ret * 10 + c - '0'; 
            }  while ((c = read()) >= '0' && c <= '9'); 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public long nextLong() throws IOException 
        { 
            long ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public double nextDouble() throws IOException 
        { 
            double ret = 0, div = 1; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
  
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
  
            if (c == '.') 
            { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        private void fillBuffer() throws IOException 
        { 
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
            if (bytesRead == -1) 
                buffer[0] = -1; 
        } 
  
        private byte read() throws IOException 
        { 
            if (bufferPointer == bytesRead) 
                fillBuffer(); 
            return buffer[bufferPointer++]; 
        } 
  
        public void close() throws IOException 
        { 
            if (din == null) 
                return; 
            din.close(); 
        } 
    } 

} Main public static void main (String[] args) throws java.lang.Exception
   {
	try{
	     //long a=Long.parseLong(next());
	    // int a=sc.nextInt();
	     Reader sc=new Reader();
	     PrintWriter out=new PrintWriter(System.out);
	     long n=sc.nextInt();
		  long x=sc.nextInt();
		  long t=sc.nextInt();
		  
		  long val=(long)Math.ceil((double)n/(double)x);
		  out.println(val*t);
		      
		      
		      
		    
	out.flush();
	out.close();
	   }     
	catch(Exception e)
		 {}
	} main {
	try{
	     //long a=Long.parseLong(next());
	    // int a=sc.nextInt();
	     Reader sc=new Reader();
	     PrintWriter out=new PrintWriter(System.out);
	     long n=sc.nextInt();
		  long x=sc.nextInt();
		  long t=sc.nextInt();
		  
		  long val=(long)Math.ceil((double)n/(double)x);
		  out.println(val*t);
		      
		      
		      
		    
	out.flush();
	out.close();
	   }     
	catch(Exception e)
		 {}
	} try{
	     //long a=Long.parseLong(next());
	    // int a=sc.nextInt();
	     Reader sc=new Reader();
	     PrintWriter out=new PrintWriter(System.out);
	     long n=sc.nextInt();
		  long x=sc.nextInt();
		  long t=sc.nextInt();
		  
		  long val=(long)Math.ceil((double)n/(double)x);
		  out.println(val*t);
		      
		      
		      
		    
	out.flush();
	out.close();
	   }     
	catch(Exception e)
		 {} catch(Exception e)
		 {} Exception e {} {
	     //long a=Long.parseLong(next());
	    // int a=sc.nextInt();
	     Reader sc=new Reader();
	     PrintWriter out=new PrintWriter(System.out);
	     long n=sc.nextInt();
		  long x=sc.nextInt();
		  long t=sc.nextInt();
		  
		  long val=(long)Math.ceil((double)n/(double)x);
		  out.println(val*t);
		      
		      
		      
		    
	out.flush();
	out.close();
	   } Reader sc=new Reader(); sc new Reader() PrintWriter out=new PrintWriter(System.out); out new PrintWriter(System.out) long n=sc.nextInt(); n sc.nextInt() sc.nextInt sc long x=sc.nextInt(); x sc.nextInt() sc.nextInt sc long t=sc.nextInt(); t sc.nextInt() sc.nextInt sc long val=(long)Math.ceil((double)n/(double)x); val (long)Math.ceil((double)n/(double)x) Math.ceil Math (double)n/(double)x (double)n (double)x out.println(val*t) out.println out val*t val t out.flush() out.flush out out.close() out.close out String[] args args static class Reader 
    { 
        final private int BUFFER_SIZE = 1 << 16; 
        private DataInputStream din; 
        private byte[] buffer; 
        private int bufferPointer, bytesRead; 
  
        public Reader() 
        { 
            din = new DataInputStream(System.in); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public Reader(String file_name) throws IOException 
        { 
            din = new DataInputStream(new FileInputStream(file_name)); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public String readLine() throws IOException 
        { 
            byte[] buf = new byte[64]; // line length 
            int cnt = 0, c; 
            while ((c = read()) != -1) 
            { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } 
            return new String(buf, 0, cnt); 
        } 
  
        public int nextInt() throws IOException 
        { 
            int ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do
            { 
                ret = ret * 10 + c - '0'; 
            }  while ((c = read()) >= '0' && c <= '9'); 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public long nextLong() throws IOException 
        { 
            long ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public double nextDouble() throws IOException 
        { 
            double ret = 0, div = 1; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
  
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
  
            if (c == '.') 
            { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        private void fillBuffer() throws IOException 
        { 
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
            if (bytesRead == -1) 
                buffer[0] = -1; 
        } 
  
        private byte read() throws IOException 
        { 
            if (bufferPointer == bytesRead) 
                fillBuffer(); 
            return buffer[bufferPointer++]; 
        } 
  
        public void close() throws IOException 
        { 
            if (din == null) 
                return; 
            din.close(); 
        } 
    } Reader final private int BUFFER_SIZE = 1 << 16; BUFFER_SIZE 1 << 16 1 16 private DataInputStream din; din private byte[] buffer; buffer private int bufferPointer bufferPointer bytesRead; bytesRead public Reader() 
        { 
            din = new DataInputStream(System.in); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } Reader { 
            din = new DataInputStream(System.in); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } din = new DataInputStream(System.in) din new DataInputStream(System.in) buffer = new byte[BUFFER_SIZE] buffer new byte[BUFFER_SIZE] BUFFER_SIZE bufferPointer = bytesRead = 0 bufferPointer bytesRead = 0 bytesRead 0 public Reader(String file_name) throws IOException 
        { 
            din = new DataInputStream(new FileInputStream(file_name)); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } Reader { 
            din = new DataInputStream(new FileInputStream(file_name)); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } din = new DataInputStream(new FileInputStream(file_name)) din new DataInputStream(new FileInputStream(file_name)) buffer = new byte[BUFFER_SIZE] buffer new byte[BUFFER_SIZE] BUFFER_SIZE bufferPointer = bytesRead = 0 bufferPointer bytesRead = 0 bytesRead 0 String file_name file_name public String readLine() throws IOException 
        { 
            byte[] buf = new byte[64]; // line length 
            int cnt = 0, c; 
            while ((c = read()) != -1) 
            { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } 
            return new String(buf, 0, cnt); 
        } readLine { 
            byte[] buf = new byte[64]; // line length 
            int cnt = 0, c; 
            while ((c = read()) != -1) 
            { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } 
            return new String(buf, 0, cnt); 
        } byte[] buf = new byte[64]; buf new byte[64] 64 int cnt = 0 cnt 0 c; c while ((c = read()) != -1) 
            { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } (c = read()) != -1 (c = read()) c read() read -1 1 { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } if (c == '\n') 
                    break; c == '\n' c '\n' break; buf[cnt++] = (byte) c buf[cnt++] buf cnt++ cnt (byte) c return new String(buf, 0, cnt); new String(buf, 0, cnt) public int nextInt() throws IOException 
        { 
            int ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do
            { 
                ret = ret * 10 + c - '0'; 
            }  while ((c = read()) >= '0' && c <= '9'); 
  
            if (neg) 
                return -ret; 
            return ret; 
        } nextInt { 
            int ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do
            { 
                ret = ret * 10 + c - '0'; 
            }  while ((c = read()) >= '0' && c <= '9'); 
  
            if (neg) 
                return -ret; 
            return ret; 
        } int ret = 0; ret 0 byte c = read(); c read() read while (c <= ' ') 
                c = read(); c <= ' ' c ' ' c = read() c read() read boolean neg = (c == '-'); neg (c == '-') c '-' if (neg) 
                c = read(); neg c = read() c read() read do
            { 
                ret = ret * 10 + c - '0'; 
            }  while ((c = read()) >= '0' && c <= '9'); (c = read()) >= '0' && c <= '9' (c = read()) >= '0' (c = read()) c read() read '0' c <= '9' c '9' { 
                ret = ret * 10 + c - '0'; 
            } ret = ret * 10 + c - '0' ret ret * 10 + c - '0' ret * 10 + c ret * 10 ret 10 c '0' if (neg) 
                return -ret; neg return -ret; -ret ret return ret; ret public long nextLong() throws IOException 
        { 
            long ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
            if (neg) 
                return -ret; 
            return ret; 
        } nextLong { 
            long ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
            if (neg) 
                return -ret; 
            return ret; 
        } long ret = 0; ret 0 byte c = read(); c read() read while (c <= ' ') 
                c = read(); c <= ' ' c ' ' c = read() c read() read boolean neg = (c == '-'); neg (c == '-') c '-' if (neg) 
                c = read(); neg c = read() c read() read do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); (c = read()) >= '0' && c <= '9' (c = read()) >= '0' (c = read()) c read() read '0' c <= '9' c '9' { 
                ret = ret * 10 + c - '0'; 
            } ret = ret * 10 + c - '0' ret ret * 10 + c - '0' ret * 10 + c ret * 10 ret 10 c '0' if (neg) 
                return -ret; neg return -ret; -ret ret return ret; ret public double nextDouble() throws IOException 
        { 
            double ret = 0, div = 1; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
  
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
  
            if (c == '.') 
            { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } 
  
            if (neg) 
                return -ret; 
            return ret; 
        } nextDouble { 
            double ret = 0, div = 1; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
  
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
  
            if (c == '.') 
            { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } 
  
            if (neg) 
                return -ret; 
            return ret; 
        } double ret = 0 ret 0 div = 1; div 1 byte c = read(); c read() read while (c <= ' ') 
                c = read(); c <= ' ' c ' ' c = read() c read() read boolean neg = (c == '-'); neg (c == '-') c '-' if (neg) 
                c = read(); neg c = read() c read() read do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); (c = read()) >= '0' && c <= '9' (c = read()) >= '0' (c = read()) c read() read '0' c <= '9' c '9' { 
                ret = ret * 10 + c - '0'; 
            } ret = ret * 10 + c - '0' ret ret * 10 + c - '0' ret * 10 + c ret * 10 ret 10 c '0' if (c == '.') 
            { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } c == '.' c '.' { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } (c = read()) >= '0' && c <= '9' (c = read()) >= '0' (c = read()) c read() read '0' c <= '9' c '9' { 
                    ret += (c - '0') / (div *= 10); 
                } ret += (c - '0') / (div *= 10) ret (c - '0') / (div *= 10) (c - '0') c '0' (div *= 10) div 10 if (neg) 
                return -ret; neg return -ret; -ret ret return ret; ret private void fillBuffer() throws IOException 
        { 
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
            if (bytesRead == -1) 
                buffer[0] = -1; 
        } fillBuffer { 
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
            if (bytesRead == -1) 
                buffer[0] = -1; 
        } bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE) bytesRead din.read(buffer, bufferPointer = 0, BUFFER_SIZE) din.read din buffer bufferPointer = 0 bufferPointer 0 BUFFER_SIZE if (bytesRead == -1) 
                buffer[0] = -1; bytesRead == -1 bytesRead -1 1 buffer[0] = -1 buffer[0] buffer 0 -1 1 private byte read() throws IOException 
        { 
            if (bufferPointer == bytesRead) 
                fillBuffer(); 
            return buffer[bufferPointer++]; 
        } read { 
            if (bufferPointer == bytesRead) 
                fillBuffer(); 
            return buffer[bufferPointer++]; 
        } if (bufferPointer == bytesRead) 
                fillBuffer(); bufferPointer == bytesRead bufferPointer bytesRead fillBuffer() fillBuffer return buffer[bufferPointer++]; buffer[bufferPointer++] buffer bufferPointer++ bufferPointer public void close() throws IOException 
        { 
            if (din == null) 
                return; 
            din.close(); 
        } close { 
            if (din == null) 
                return; 
            din.close(); 
        } if (din == null) 
                return; din == null din null return; din.close() din.close din public class Main
{ 
   
  public static void main (String[] args) throws java.lang.Exception
   {
	try{
	     //long a=Long.parseLong(next());
	    // int a=sc.nextInt();
	     Reader sc=new Reader();
	     PrintWriter out=new PrintWriter(System.out);
	     long n=sc.nextInt();
		  long x=sc.nextInt();
		  long t=sc.nextInt();
		  
		  long val=(long)Math.ceil((double)n/(double)x);
		  out.println(val*t);
		      
		      
		      
		    
	out.flush();
	out.close();
	   }     
	catch(Exception e)
		 {}
	}
	//Template
  // static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
   //  static PrintWriter pw = new PrintWriter(System.out);
   //  static StringTokenizer st;
    
   //  static String next()
   //     {
   //          while(st==null || !st.hasMoreElements()) 
   //          {
   //              try
   //              {
   //                 st = new StringTokenizer(br.readLine());
   //              }
   //              catch(IOException e)
   //              {
   //                 e.printStackTrace();
   //              }
   //          }
   //          return st.nextToken();
   //     }
   // static int gcd(int a,int b)
   //  {
   //     if(b==0)
   //     return a;
   //     else
   //     return gcd(b,a%b);
   //  }
   
    static class Reader 
    { 
        final private int BUFFER_SIZE = 1 << 16; 
        private DataInputStream din; 
        private byte[] buffer; 
        private int bufferPointer, bytesRead; 
  
        public Reader() 
        { 
            din = new DataInputStream(System.in); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public Reader(String file_name) throws IOException 
        { 
            din = new DataInputStream(new FileInputStream(file_name)); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public String readLine() throws IOException 
        { 
            byte[] buf = new byte[64]; // line length 
            int cnt = 0, c; 
            while ((c = read()) != -1) 
            { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } 
            return new String(buf, 0, cnt); 
        } 
  
        public int nextInt() throws IOException 
        { 
            int ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do
            { 
                ret = ret * 10 + c - '0'; 
            }  while ((c = read()) >= '0' && c <= '9'); 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public long nextLong() throws IOException 
        { 
            long ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public double nextDouble() throws IOException 
        { 
            double ret = 0, div = 1; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
  
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
  
            if (c == '.') 
            { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        private void fillBuffer() throws IOException 
        { 
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
            if (bytesRead == -1) 
                buffer[0] = -1; 
        } 
  
        private byte read() throws IOException 
        { 
            if (bufferPointer == bytesRead) 
                fillBuffer(); 
            return buffer[bufferPointer++]; 
        } 
  
        public void close() throws IOException 
        { 
            if (din == null) 
                return; 
            din.close(); 
        } 
    } 

} public class Main
{ 
   
  public static void main (String[] args) throws java.lang.Exception
   {
	try{
	     //long a=Long.parseLong(next());
	    // int a=sc.nextInt();
	     Reader sc=new Reader();
	     PrintWriter out=new PrintWriter(System.out);
	     long n=sc.nextInt();
		  long x=sc.nextInt();
		  long t=sc.nextInt();
		  
		  long val=(long)Math.ceil((double)n/(double)x);
		  out.println(val*t);
		      
		      
		      
		    
	out.flush();
	out.close();
	   }     
	catch(Exception e)
		 {}
	}
	//Template
  // static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
   //  static PrintWriter pw = new PrintWriter(System.out);
   //  static StringTokenizer st;
    
   //  static String next()
   //     {
   //          while(st==null || !st.hasMoreElements()) 
   //          {
   //              try
   //              {
   //                 st = new StringTokenizer(br.readLine());
   //              }
   //              catch(IOException e)
   //              {
   //                 e.printStackTrace();
   //              }
   //          }
   //          return st.nextToken();
   //     }
   // static int gcd(int a,int b)
   //  {
   //     if(b==0)
   //     return a;
   //     else
   //     return gcd(b,a%b);
   //  }
   
    static class Reader 
    { 
        final private int BUFFER_SIZE = 1 << 16; 
        private DataInputStream din; 
        private byte[] buffer; 
        private int bufferPointer, bytesRead; 
  
        public Reader() 
        { 
            din = new DataInputStream(System.in); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public Reader(String file_name) throws IOException 
        { 
            din = new DataInputStream(new FileInputStream(file_name)); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public String readLine() throws IOException 
        { 
            byte[] buf = new byte[64]; // line length 
            int cnt = 0, c; 
            while ((c = read()) != -1) 
            { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } 
            return new String(buf, 0, cnt); 
        } 
  
        public int nextInt() throws IOException 
        { 
            int ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do
            { 
                ret = ret * 10 + c - '0'; 
            }  while ((c = read()) >= '0' && c <= '9'); 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public long nextLong() throws IOException 
        { 
            long ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public double nextDouble() throws IOException 
        { 
            double ret = 0, div = 1; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
  
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
  
            if (c == '.') 
            { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        private void fillBuffer() throws IOException 
        { 
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
            if (bytesRead == -1) 
                buffer[0] = -1; 
        } 
  
        private byte read() throws IOException 
        { 
            if (bufferPointer == bytesRead) 
                fillBuffer(); 
            return buffer[bufferPointer++]; 
        } 
  
        public void close() throws IOException 
        { 
            if (din == null) 
                return; 
            din.close(); 
        } 
    } 

} Main
/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class Main
{ 
   
  public static void main (String[] args) throws java.lang.Exception
   {
	try{
	     //long a=Long.parseLong(next());
	    // int a=sc.nextInt();
	     Reader sc=new Reader();
	     PrintWriter out=new PrintWriter(System.out);
	     long n=sc.nextInt();
		  long x=sc.nextInt();
		  long t=sc.nextInt();
		  
		  long val=(long)Math.ceil((double)n/(double)x);
		  out.println(val*t);
		      
		      
		      
		    
	out.flush();
	out.close();
	   }     
	catch(Exception e)
		 {}
	}
	//Template
  // static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
   //  static PrintWriter pw = new PrintWriter(System.out);
   //  static StringTokenizer st;
    
   //  static String next()
   //     {
   //          while(st==null || !st.hasMoreElements()) 
   //          {
   //              try
   //              {
   //                 st = new StringTokenizer(br.readLine());
   //              }
   //              catch(IOException e)
   //              {
   //                 e.printStackTrace();
   //              }
   //          }
   //          return st.nextToken();
   //     }
   // static int gcd(int a,int b)
   //  {
   //     if(b==0)
   //     return a;
   //     else
   //     return gcd(b,a%b);
   //  }
   
    static class Reader 
    { 
        final private int BUFFER_SIZE = 1 << 16; 
        private DataInputStream din; 
        private byte[] buffer; 
        private int bufferPointer, bytesRead; 
  
        public Reader() 
        { 
            din = new DataInputStream(System.in); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public Reader(String file_name) throws IOException 
        { 
            din = new DataInputStream(new FileInputStream(file_name)); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public String readLine() throws IOException 
        { 
            byte[] buf = new byte[64]; // line length 
            int cnt = 0, c; 
            while ((c = read()) != -1) 
            { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } 
            return new String(buf, 0, cnt); 
        } 
  
        public int nextInt() throws IOException 
        { 
            int ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do
            { 
                ret = ret * 10 + c - '0'; 
            }  while ((c = read()) >= '0' && c <= '9'); 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public long nextLong() throws IOException 
        { 
            long ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public double nextDouble() throws IOException 
        { 
            double ret = 0, div = 1; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
  
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
  
            if (c == '.') 
            { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        private void fillBuffer() throws IOException 
        { 
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
            if (bytesRead == -1) 
                buffer[0] = -1; 
        } 
  
        private byte read() throws IOException 
        { 
            if (bufferPointer == bytesRead) 
                fillBuffer(); 
            return buffer[bufferPointer++]; 
        } 
  
        public void close() throws IOException 
        { 
            if (din == null) 
                return; 
            din.close(); 
        } 
    } 

}
