Tourist Shop

#include <iostream>
#include <string>

using namespace std;

int main() {
    double budget, price, totalSum = 0;
    cin >> budget;
    cin.ignore();

    string product;
    getline(cin, product);

    int counter = 0;

    while (product != "Stop") {
        cin >> price;
        cin.ignore();
        counter++;

        if (counter % 3 == 0) {
            price /= 2;
        }
        totalSum += price;

        if (budget < totalSum) {
            break;
        }
        getline(cin, product);
    }

    cout.setf(ios::fixed);
    cout.precision(2);

    if (product == "Stop") {
        cout << "You bought " << counter << " products for " << totalSum << " leva.\n";
    }
    else {
        cout << "You don't have enough money!\n"
            << "You need " << totalSum - budget << " leva!\n";
    }

    return 0;
}

Решение с for и printf():

#include <iostream>
#include <string>

using namespace std;

int main() {
    double budget, price, totalSum = 0;
    cin >> budget;
    cin.ignore();

    string product;
    getline(cin, product);

    for (int i = 1; i < 2147483647; i++) {
        if (product == "Stop") {
            printf("You bought %i products for %.2f leva.\n", --i, totalSum);
            return 0;
        }
        cin >> price;
        cin.ignore();

        if (i % 3 == 0) {
            price /= 2;
        }
        totalSum += price;

        if (budget < totalSum) {
            printf("You don't have enough money!\nYou need %.2f leva!\n", totalSum - budget);
            return 0;
        }
        getline(cin, product);
    }
}