import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n, x, t;
        n = sc.nextInt();
        x = sc.nextInt();
        t = sc.nextInt();
        long ans = 0, tako = 0;
        while (n > tako) {
            ans += t;
            tako += x;
        }
        System.out.println(ans);
        sc.close();
    }
}
/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