import java.util.*;
import java.io.*;
public class Main
{
    public static void main(String args[])throws Exception
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw=new PrintWriter(System.out);
        String str[]=br.readLine().split(" ");
        int n=Integer.parseInt(str[0]);
        int x=Integer.parseInt(str[1]);
        int t=Integer.parseInt(str[2]);
        pw.println((int)Math.ceil((double)n/x)*t);
        pw.flush();
        pw.close();
    }
} import java.util.*; util.* java import java.io.*; io.* java public class Main
{
    public static void main(String args[])throws Exception
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw=new PrintWriter(System.out);
        String str[]=br.readLine().split(" ");
        int n=Integer.parseInt(str[0]);
        int x=Integer.parseInt(str[1]);
        int t=Integer.parseInt(str[2]);
        pw.println((int)Math.ceil((double)n/x)*t);
        pw.flush();
        pw.close();
    }
} Main public static void main(String args[])throws Exception
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw=new PrintWriter(System.out);
        String str[]=br.readLine().split(" ");
        int n=Integer.parseInt(str[0]);
        int x=Integer.parseInt(str[1]);
        int t=Integer.parseInt(str[2]);
        pw.println((int)Math.ceil((double)n/x)*t);
        pw.flush();
        pw.close();
    } main {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw=new PrintWriter(System.out);
        String str[]=br.readLine().split(" ");
        int n=Integer.parseInt(str[0]);
        int x=Integer.parseInt(str[1]);
        int t=Integer.parseInt(str[2]);
        pw.println((int)Math.ceil((double)n/x)*t);
        pw.flush();
        pw.close();
    } BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) PrintWriter pw=new PrintWriter(System.out); pw new PrintWriter(System.out) String str[]=br.readLine().split(" "); str br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " int n=Integer.parseInt(str[0]); n Integer.parseInt(str[0]) Integer.parseInt Integer str[0] str 0 int x=Integer.parseInt(str[1]); x Integer.parseInt(str[1]) Integer.parseInt Integer str[1] str 1 int t=Integer.parseInt(str[2]); t Integer.parseInt(str[2]) Integer.parseInt Integer str[2] str 2 pw.println((int)Math.ceil((double)n/x)*t) pw.println pw (int)Math.ceil((double)n/x)*t (int)Math.ceil((double)n/x) Math.ceil Math (double)n/x (double)n x t pw.flush() pw.flush pw pw.close() pw.close pw String args[] args public class Main
{
    public static void main(String args[])throws Exception
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw=new PrintWriter(System.out);
        String str[]=br.readLine().split(" ");
        int n=Integer.parseInt(str[0]);
        int x=Integer.parseInt(str[1]);
        int t=Integer.parseInt(str[2]);
        pw.println((int)Math.ceil((double)n/x)*t);
        pw.flush();
        pw.close();
    }
} public class Main
{
    public static void main(String args[])throws Exception
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw=new PrintWriter(System.out);
        String str[]=br.readLine().split(" ");
        int n=Integer.parseInt(str[0]);
        int x=Integer.parseInt(str[1]);
        int t=Integer.parseInt(str[2]);
        pw.println((int)Math.ceil((double)n/x)*t);
        pw.flush();
        pw.close();
    }
} Main
import java.util.*;
import java.io.*;
public class Main
{
    public static void main(String args[])throws Exception
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw=new PrintWriter(System.out);
        String str[]=br.readLine().split(" ");
        int n=Integer.parseInt(str[0]);
        int x=Integer.parseInt(str[1]);
        int t=Integer.parseInt(str[2]);
        pw.println((int)Math.ceil((double)n/x)*t);
        pw.flush();
        pw.close();
    }
}