3. Simple Calculator

#include <iostream>
#include <string>
#include <queue>
#include <sstream>

using namespace std;

int main() {
    string line, s;
    getline(cin, line);

    istringstream ss(line);

    queue<int> numbers;
    queue<string> expressions;
    int counter = 0;

    while (ss >> s) {
        if (counter % 2 == 0) {
            numbers.push(stoi(s));
        }
        else {
            expressions.push(s);
        }
        counter++;
    }

    int sum = numbers.front();
    numbers.pop();

    while (!expressions.empty()) {

        if (expressions.front() == "+") {
            sum += numbers.front();
        }
        else {
            sum -= numbers.front();
        }

        expressions.pop();
        numbers.pop();
    }

    while (!numbers.empty()) {
        sum += numbers.front();
        numbers.pop();
    }

    cout << sum << endl;
    return 0;
}