import java.util.*;
class Main
{
  public static void main(String args[])
  {
    int n,x,t,k;
    Scanner sc= new Scanner(System.in);
    n=sc.nextInt();
    x=sc.nextInt();
    t=sc.nextInt();
    k=n/x;
    if(n%x>0)
      k+=1;
    System.out.println(k*t);
  }
}
/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