import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        
        int time;
        
        if(n % x == 0){
            time = n / x * t;
        } else {
            time = (n / x + 1) * t;
        }
        
        System.out.println(time);
    }
}
/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