import java.util.*;
public class Main{
  public static void main(String arg[])
  {
   Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    int x=sc.nextInt();
    int t=sc.nextInt();
    
    int a=0;
    while(n>0)
    {
       a+=t;
       n-=x;
    }
    
    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