import java.util.*;

public class Main{
	public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
      int n= sc.nextInt();
      int x =sc.nextInt();
      int t =sc.nextInt();
      
      int c;
      int a;
      c = (n+x-1)/x;
      a = c*t;
      System.out.println(a);
      
    }
}
/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