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

public class Main{
	public static void main (String[] args) {
		//code
		Scanner in=new Scanner(System.in);
		int n,x,t;
      	n=in.nextInt();
      	x=in.nextInt();
      	t=in.nextInt();
      	int ans=(int)Math.ceil((double)n/x)*t;
      	System.out.println(ans);
	}
} import java.util.*; util.* java import java.lang.*; lang.* java import java.io.*; io.* java public class Main{
	public static void main (String[] args) {
		//code
		Scanner in=new Scanner(System.in);
		int n,x,t;
      	n=in.nextInt();
      	x=in.nextInt();
      	t=in.nextInt();
      	int ans=(int)Math.ceil((double)n/x)*t;
      	System.out.println(ans);
	}
} Main public static void main (String[] args) {
		//code
		Scanner in=new Scanner(System.in);
		int n,x,t;
      	n=in.nextInt();
      	x=in.nextInt();
      	t=in.nextInt();
      	int ans=(int)Math.ceil((double)n/x)*t;
      	System.out.println(ans);
	} main {
		//code
		Scanner in=new Scanner(System.in);
		int n,x,t;
      	n=in.nextInt();
      	x=in.nextInt();
      	t=in.nextInt();
      	int ans=(int)Math.ceil((double)n/x)*t;
      	System.out.println(ans);
	} Scanner in=new Scanner(System.in); in new Scanner(System.in) int n n x x t; t n=in.nextInt() n in.nextInt() in.nextInt in x=in.nextInt() x in.nextInt() in.nextInt in t=in.nextInt() t in.nextInt() in.nextInt in int ans=(int)Math.ceil((double)n/x)*t; ans (int)Math.ceil((double)n/x)*t (int)Math.ceil((double)n/x) Math.ceil Math (double)n/x (double)n x t System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main{
	public static void main (String[] args) {
		//code
		Scanner in=new Scanner(System.in);
		int n,x,t;
      	n=in.nextInt();
      	x=in.nextInt();
      	t=in.nextInt();
      	int ans=(int)Math.ceil((double)n/x)*t;
      	System.out.println(ans);
	}
} public class Main{
	public static void main (String[] args) {
		//code
		Scanner in=new Scanner(System.in);
		int n,x,t;
      	n=in.nextInt();
      	x=in.nextInt();
      	t=in.nextInt();
      	int ans=(int)Math.ceil((double)n/x)*t;
      	System.out.println(ans);
	}
} Main
import java.util.*;
import java.lang.*;
import java.io.*;

public class Main{
	public static void main (String[] args) {
		//code
		Scanner in=new Scanner(System.in);
		int n,x,t;
      	n=in.nextInt();
      	x=in.nextInt();
      	t=in.nextInt();
      	int ans=(int)Math.ceil((double)n/x)*t;
      	System.out.println(ans);
	}
}
