import java.util.Scanner;

public class Main {
	public static void main(String [] args) {
    	Scanner sn = new Scanner(System.in);
      	int n = sn.nextInt();
      	int x = sn.nextInt();
      	int t = sn.nextInt();
      	int res = n / x;
      	int mod = n % x;
      	if(mod != 0) {
        	res++;
        }
      	res = res * t; 
        System.out.println(res);
    }
}
/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