#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
        cout << "Please input a non-negative whole number: ";
        int n {0};
        cin >> n;

	if (!cin) {
		cerr << "Sorry, that wasn't a number.\n";
		return EXIT_FAILURE;
	}

	if (n < 0) {
		cerr << "Sorry, the number can't be negative.\n";
		return EXIT_FAILURE;
	}

        int lastDigit {n % 10};      //the rightmost digit of n
        int lastTwoDigits {n % 100};

	cout << "The ordinal form of " << n << " is " << n;

        if (11 <= lastTwoDigits && lastTwoDigits <= 19) {   //in the teens
                cout << "th";
	} else if (lastDigit == 1) {
                cout << "st";
        } else if (lastDigit == 2) {
                cout << "nd";
        } else if (lastDigit == 3) {
                cout << "rd";
        } else {
                cout << "th"; //none of the above
        }

        cout << ".\n";        //Period at the end of the sentence.
        return EXIT_SUCCESS;
}