import java.io.PrintWriter;
import java.util.Scanner;

public class Main {
    void solve(Scanner sc, PrintWriter pw) {
        int N = sc.nextInt();
        int X = sc.nextInt();
        int T = sc.nextInt();
        pw.println((N + X - 1) / X * T);
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        new Main().solve(sc, pw);
        pw.flush();
        pw.close();
        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