// Simple example of input validation.
#include <iostream>
using namespace std;

int main()
{
    const int LOWER_BOUND = 0;
    const int UPPER_BOUND = 100;
    int num;

    cout << "Enter a number between " << LOWER_BOUND 
         << " and " << UPPER_BOUND << ": ";
    cin >> num;

    // Fall through loop only if input is valid.
    while (num < LOWER_BOUND || num > UPPER_BOUND)
    {
        cout << "Enter a number between " << LOWER_BOUND
             << " and " << UPPER_BOUND << ": ";
        cin >> num;
    }

    cout << "Congratulations, you can follow directions." << endl;

    return 0;
}