import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		// 整数の入力
		int n = sc.nextInt();
		int x = sc.nextInt();
		int t = sc.nextInt();

		int makeNum = 0;
		int num = 0;

		while(makeNum < n){
			makeNum = makeNum + x;
			num = num + t;
		}

		System.out.println(num);

		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