import java.util.*;
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 u=0,t1=0;
    while(u<n){
      t1=t1+t;
      u=u+x;
    }
    System.out.println(t1);
  }}
/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