import java.util.*;
import java.io.*;
public class Main
{
	public static void main(String args[]) throws IOException
	{
		
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		int n,x,t=0;
		String brr[]=br.readLine().split(" ");
		n=Integer.parseInt(brr[0]);
		x=Integer.parseInt(brr[1]);
		t=Integer.parseInt(brr[2]);
		long ans=0;
		while(n>0)
		{
		ans+=t;
        n-=x;
		}
		System.out.println(ans);
	}
}		
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz