Thread: What happens if...?

That's because std::cin does input validation. You'll need to check the result of an input operation, and if there was a problem "ignore" unread characters and "clear" the error bits.

Code:

#include <iostream>
#include <limits>

int main()
{
    int n = 1;
    do {
        if (std::cin >> n) {
            std::cout << "Ok " << n << '\n';
        }
        else {
            std::cout << "Not Ok\n";
            std::cin.clear();
            std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
        }
    } while (n);
}