#include <iostream>

//#define NDEBUG
#include <cassert>

using namespace std;

/**
 * Print a nonnegative value.
 * @param n the value which must be >= 0.
 */
void print_nonnegative(int n);

int main()
{
    int n;

    do
    {
        cout << endl << "Value? ";
        cin >> n;
        print_nonnegative(n);
    } while (n > 0);

    cout << endl << "Done!" << endl;
    return 0;
}

void print_nonnegative(int n)
{
    assert(n >= 0);
    cout << "You entered value " << n << endl;
}