import java.util.*;

public class Main {
	public static void main(String[] args){
 
        Scanner sc = null;
        sc = new Scanner(System.in);
        int n = sc.nextInt();
        int x = sc.nextInt();
        int t = sc.nextInt();
        sc.close();
        int ans = 0;

        for (int i = 0; i < 1000; i++) {

            ans += t;
            n -= x;
            if (n <= 0) {
                break;
            }
        }

        System.out.println(ans);   
      }
}
/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