int num1 = 0;
cin >> num1;

while (cin.fail()) {
    cout << "Enter a valid number for num1";
    cin.clear();
    cin.ignore(256, 'n');
    cin >> num;
}

int num2 = 0;
cin >> num2;

while (cin.fail()) {
    cout << "Enter a valid number for num2 ";
    cin.clear();
    cin.ignore(256, 'n');
    cin >> num;
}