import java.util.Scanner;

public class Main{
public static void main(String[]  args){
  Scanner stdIn = new Scanner(System.in);
   int n = stdIn.nextInt();
   int x = stdIn.nextInt();
   int t = stdIn.nextInt();
  
  if(n%x == 0){System.out.println(t*(n/x));}
  else {System.out.println(t*(n/x + 1));}
  
}
}
/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