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

int main()
{
	double fahrenheit {0};
	cout << "What temperature is it in Fahrenheit (input the number only)?\n";
	cin >> fahrenheit;

	if (!cin) {
		cerr << "Sorry, that wasn't a valid whole number.\n";
		return EXIT_FAILURE;   //fahrenheit dies here; celsius not born yet.
	}

	
	double celsius {(fahrenheit - 32) * (5.0/9.0)};


	cout << "That is "
		<< celsius << " degrees Celsius.\n";

	return EXIT_SUCCESS;   //fahrenheit and celsius die here.
}