import java.util.*;

public class Main {

    public static void main(String args[]) {


        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int x = scan.nextInt();
        int t = scan.nextInt();

        int a = n / x;

        int b = n % x;
        if (b != 0) {
            System.out.println(t * (a + 1));
            
        } else {

            System.out.println(t * a);
            
        }
        
    }
}
/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