import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Main
{
 public static void main(String args[])
  {
    Scanner sc=new Scanner(System.in);
    int n=sc.nextInt(),x=sc.nextInt(),t=sc.nextInt();
    int a;
    if(n%x==0) a=n/x;
    else a=n/x+1;
    System.out.println(a*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