Tourist Shop

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double budget = Double.parseDouble(scanner.nextLine()),
                price, totalSum = 0;
        int counter = 0;
        String product;
        while (!(product = scanner.nextLine()).equals("Stop")) {
            price = Double.parseDouble(scanner.nextLine());
            counter++;
            if (counter % 3 == 0) {
                price /= 2;
            }
            totalSum += price;
            if (budget < totalSum) {
                break;
            }
        }

        if (product.equals("Stop")) {
            System.out.printf("You bought %d products for %.2f leva.\n", counter, totalSum);
        } else {
            System.out.printf("You don't have enough money!\nYou need %.2f leva!\n", totalSum - budget);
        }
    }
}

ИЛИ:

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double budget = Double.parseDouble(scanner.nextLine()),
                price, totalSum = 0;
        String product;

        for (int i = 1; i < 2147483647; i++) {
            if ((product = scanner.nextLine()).equals("Stop")) {
                System.out.printf("You bought %d products for %.2f leva.\n", --i, totalSum);
                return;
            }
            price = Double.parseDouble(scanner.nextLine());
            if (i % 3 == 0) {
                price /= 2;
            }
            totalSum += price;
            if (budget < totalSum) {
                System.out.printf("You don't have enough money!\nYou need %.2f leva!\n", totalSum - budget);
                return;
            }
        }
    }
}