A. 顛倒國 (reverse)

#include <bits/stdc++.h>
using namespace std;

int main() {
    string formula;
    getline(cin, formula);
    reverse(formula.begin(), formula.end());

    stringstream ss;
    string formula_add_sub, L, op, R;

    ss << formula;
    ss >> L;
    while (ss >> op >> R) {
        if (op == "+" or op == "-") formula_add_sub += L + " " + op + " ", L = R;
        else if (op == "*")  L = to_string( stoi(L) * stoi(R) );
        else if (op == "\\") L = to_string( stoi(L) / stoi(R) );
    }
    formula_add_sub += L;

    ss.clear();
    ss << formula_add_sub;
    ss >> L;
    while (ss >> op >> R) {
             if (op == "+") L = to_string( stoi(L) + stoi(R) );
        else if (op == "-") L = to_string( stoi(L) - stoi(R) );
    }

    cout << L << "\n";

    return 0;
}