import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public 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 times = n/x;
    if(n % x != 0){
      times++;
    }
    
    System.out.println(times * t);

    return;

  }
}
/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