很无脑但是可行

Java

import java.util.Scanner;

public class Main {
        public static void main(String[] args) {
            Scanner scanner = new Scanner(System.in);
            short n = scanner.nextShort();
            short a1 = scanner.nextShort(), a2 = scanner.nextShort();
            short b1 = scanner.nextShort(), b2 = scanner.nextShort();
            short c1 = scanner.nextShort(), c2 = scanner.nextShort();

            int price1 = ((int) Math.ceil((double) n / a1)) * a2;
            int price2 = ((int) Math.ceil((double) n / b1)) * b2;
            int price3 = ((int) Math.ceil((double) n / c1)) * c2;

            System.out.println(Math.min(price1, Math.min(price2, price3)));
        }
    }

比较正常的解法：

看起来比较整活的解法：