import java.util.Scanner;

public class Main {
    static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
        int n = sc.nextInt(), x = sc.nextInt(), t = sc.nextInt();
        int ans = n/x + Math.min(n%x , 1);
        System.out.println(ans*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