import java.io.*;
import java.util.*;
import java.math.BigInteger;
public class Main {
	
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter syso = new PrintWriter(System.out);
		double n=sc.nextDouble();
		double a=sc.nextDouble();
		int t=sc.nextInt();
		int ans=(int)Math.ceil(n/a);
		syso.println(ans*t);
        syso.close();
    }
    
 
	static class Scanner {
		StringTokenizer st;
		BufferedReader br;
 
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
 
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
 
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
 
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
 
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
 
		public String nextLine() throws IOException {
			return br.readLine();
		}
 
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
 
		public boolean ready() throws IOException {
			return br.ready();
		}
		public int[] nextArr(int n) throws IOException{
			int arr[]=new int[n];
			for(int i=0;i<n;i++)arr[i]=nextInt();
			return arr;
		}
		public BigInteger BigInteger(String s) throws IOException{
			BigInteger a=new BigInteger(s);
			return a;
		}
 
	}
} import java.io.*; io.* java import java.util.*; util.* java import java.math.BigInteger; BigInteger java.math public class Main {
	
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter syso = new PrintWriter(System.out);
		double n=sc.nextDouble();
		double a=sc.nextDouble();
		int t=sc.nextInt();
		int ans=(int)Math.ceil(n/a);
		syso.println(ans*t);
        syso.close();
    }
    
 
	static class Scanner {
		StringTokenizer st;
		BufferedReader br;
 
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
 
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
 
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
 
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
 
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
 
		public String nextLine() throws IOException {
			return br.readLine();
		}
 
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
 
		public boolean ready() throws IOException {
			return br.ready();
		}
		public int[] nextArr(int n) throws IOException{
			int arr[]=new int[n];
			for(int i=0;i<n;i++)arr[i]=nextInt();
			return arr;
		}
		public BigInteger BigInteger(String s) throws IOException{
			BigInteger a=new BigInteger(s);
			return a;
		}
 
	}
} Main public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter syso = new PrintWriter(System.out);
		double n=sc.nextDouble();
		double a=sc.nextDouble();
		int t=sc.nextInt();
		int ans=(int)Math.ceil(n/a);
		syso.println(ans*t);
        syso.close();
    } main {
		Scanner sc = new Scanner(System.in);
		PrintWriter syso = new PrintWriter(System.out);
		double n=sc.nextDouble();
		double a=sc.nextDouble();
		int t=sc.nextInt();
		int ans=(int)Math.ceil(n/a);
		syso.println(ans*t);
        syso.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) PrintWriter syso = new PrintWriter(System.out); syso new PrintWriter(System.out) double n=sc.nextDouble(); n sc.nextDouble() sc.nextDouble sc double a=sc.nextDouble(); a sc.nextDouble() sc.nextDouble sc int t=sc.nextInt(); t sc.nextInt() sc.nextInt sc int ans=(int)Math.ceil(n/a); ans (int)Math.ceil(n/a) Math.ceil Math n/a n a syso.println(ans*t) syso.println syso ans*t ans t syso.close() syso.close syso String[] args args static class Scanner {
		StringTokenizer st;
		BufferedReader br;
 
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
 
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
 
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
 
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
 
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
 
		public String nextLine() throws IOException {
			return br.readLine();
		}
 
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
 
		public boolean ready() throws IOException {
			return br.ready();
		}
		public int[] nextArr(int n) throws IOException{
			int arr[]=new int[n];
			for(int i=0;i<n;i++)arr[i]=nextInt();
			return arr;
		}
		public BigInteger BigInteger(String s) throws IOException{
			BigInteger a=new BigInteger(s);
			return a;
		}
 
	} Scanner StringTokenizer st; st BufferedReader br; br public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		} Scanner {
			br = new BufferedReader(new InputStreamReader(s));
		} br = new BufferedReader(new InputStreamReader(s)) br new BufferedReader(new InputStreamReader(s)) InputStream s s public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		} Scanner {
			br = new BufferedReader(new FileReader(file));
		} br = new BufferedReader(new FileReader(file)) br new BufferedReader(new FileReader(file)) String file file public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		} next {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		} while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine()); st == null || !st.hasMoreTokens() st == null st null !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st public int nextInt() throws IOException {
			return Integer.parseInt(next());
		} nextInt {
			return Integer.parseInt(next());
		} return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next public long nextLong() throws IOException {
			return Long.parseLong(next());
		} nextLong {
			return Long.parseLong(next());
		} return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next public String nextLine() throws IOException {
			return br.readLine();
		} nextLine {
			return br.readLine();
		} return br.readLine(); br.readLine() br.readLine br public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		} nextDouble {
			return Double.parseDouble(next());
		} return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next public boolean ready() throws IOException {
			return br.ready();
		} ready {
			return br.ready();
		} return br.ready(); br.ready() br.ready br public int[] nextArr(int n) throws IOException{
			int arr[]=new int[n];
			for(int i=0;i<n;i++)arr[i]=nextInt();
			return arr;
		} nextArr {
			int arr[]=new int[n];
			for(int i=0;i<n;i++)arr[i]=nextInt();
			return arr;
		} int arr[]=new int[n]; arr new int[n] n for(int i=0;i<n;i++)arr[i]=nextInt(); int i=0; int i=0; i 0 i<n i n i++ i++ i arr[i]=nextInt(); arr[i]=nextInt() arr[i] arr i nextInt() nextInt return arr; arr int n n public BigInteger BigInteger(String s) throws IOException{
			BigInteger a=new BigInteger(s);
			return a;
		} BigInteger {
			BigInteger a=new BigInteger(s);
			return a;
		} BigInteger a=new BigInteger(s); a new BigInteger(s) return a; a String s s public class Main {
	
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter syso = new PrintWriter(System.out);
		double n=sc.nextDouble();
		double a=sc.nextDouble();
		int t=sc.nextInt();
		int ans=(int)Math.ceil(n/a);
		syso.println(ans*t);
        syso.close();
    }
    
 
	static class Scanner {
		StringTokenizer st;
		BufferedReader br;
 
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
 
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
 
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
 
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
 
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
 
		public String nextLine() throws IOException {
			return br.readLine();
		}
 
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
 
		public boolean ready() throws IOException {
			return br.ready();
		}
		public int[] nextArr(int n) throws IOException{
			int arr[]=new int[n];
			for(int i=0;i<n;i++)arr[i]=nextInt();
			return arr;
		}
		public BigInteger BigInteger(String s) throws IOException{
			BigInteger a=new BigInteger(s);
			return a;
		}
 
	}
} public class Main {
	
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter syso = new PrintWriter(System.out);
		double n=sc.nextDouble();
		double a=sc.nextDouble();
		int t=sc.nextInt();
		int ans=(int)Math.ceil(n/a);
		syso.println(ans*t);
        syso.close();
    }
    
 
	static class Scanner {
		StringTokenizer st;
		BufferedReader br;
 
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
 
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
 
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
 
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
 
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
 
		public String nextLine() throws IOException {
			return br.readLine();
		}
 
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
 
		public boolean ready() throws IOException {
			return br.ready();
		}
		public int[] nextArr(int n) throws IOException{
			int arr[]=new int[n];
			for(int i=0;i<n;i++)arr[i]=nextInt();
			return arr;
		}
		public BigInteger BigInteger(String s) throws IOException{
			BigInteger a=new BigInteger(s);
			return a;
		}
 
	}
} Main
import java.io.*;
import java.util.*;
import java.math.BigInteger;
public class Main {
	
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		PrintWriter syso = new PrintWriter(System.out);
		double n=sc.nextDouble();
		double a=sc.nextDouble();
		int t=sc.nextInt();
		int ans=(int)Math.ceil(n/a);
		syso.println(ans*t);
        syso.close();
    }
    
 
	static class Scanner {
		StringTokenizer st;
		BufferedReader br;
 
		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}
 
		public Scanner(String file) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(file));
		}
 
		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
 
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
 
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
 
		public String nextLine() throws IOException {
			return br.readLine();
		}
 
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
 
		public boolean ready() throws IOException {
			return br.ready();
		}
		public int[] nextArr(int n) throws IOException{
			int arr[]=new int[n];
			for(int i=0;i<n;i++)arr[i]=nextInt();
			return arr;
		}
		public BigInteger BigInteger(String s) throws IOException{
			BigInteger a=new BigInteger(s);
			return a;
		}
 
	}
}