1. TryParse

#include <iostream>
#include <string>

using namespace std;

bool isNumber(const string& s) {
    if (s[0] != '-' && !isdigit(s[0])) {
        return false;
    }
    for (size_t i = 1; i < s.size(); i++) {
        if (!isdigit(s[i])) {
            return false;
        }
    }
    return true;
}

int main()
{
    string n1, n2;
    cin >> n1 >> n2;

    if (isNumber(n1) && isNumber(n2)) {
        cout << stoi(n1) + stoi(n2) << endl;
   }
    else {
        for (auto& n : { n1, n2 }) {
            cout << (!isNumber(n) ? "[error] " : "") << n << endl;
        }
    }

    return 0;
}