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

int main()
{
	int miles {0};
	cout << "How many miles are you going?\n";
	cin >> miles;
	
	if (!cin) {
		cerr << "Sorry, that wasn't a valid whole number.\n";
		return EXIT_FAILURE;
	}

	if (miles < 1) {
		cerr << "Sorry, the mileage must be at least 1 mile.\n";
		return EXIT_FAILURE;
	}

	const double cost {3 + .7 * .5 * miles};

	cout << "The taxi ride will cost $" << cost << " for " << miles << " miles. Thank you for riding with us.\n";

	return EXIT_SUCCESS;
}