#include <iostream>
#include <iomanip>

using namespace std;
int main()
{
	for (int execution = 1; execution <= 2; execution++)
	{
		double beginningRead, endingRead, reqGallons, avgMPG, price1, price2, price3, avgPPG, OneMileTrip;
		char answer = 'y';
		double totalMiles = 0, gallonsPurchased = 0;
		int count = 0;
		
		while (answer == 'y' || answer == 'Y')
		{
			first:
			
			cout << "Enter the beginning odomerter reading: ";
			cin >> beginningRead;
			if (count != 0 && beginningRead <= endingRead)
			{
				cout << "Your beginning odometer reading must be greater than the prior ending odometer reading.\n";
				goto first;
			}
			count++,
			
			cout << "Enter the ending odometer reading: ";
			cin >> endingRead;
			if (endingRead < beginningRead)
			{
				cout << "The ending odometer reading must be greater than the beginning odometer reading.\n";
				goto first;
			}
			
			second:
			cout << "Enter the gallons required for your full-up: ";
			cin >> reqGallons;
			if (reqGallons <= 0)
			{
				cout << "The required amount of gallons must be greater than 0.\n";
				goto second;
			}
			
			totalMiles += (endingRead - beginningRead);
			gallonsPurchased += reqGallons;
		
			cout << "Enter y to enter more readings or n to continue: ";
			cin >> answer;
		} 
		
		cout << "\n";
		avgMPG = totalMiles/gallonsPurchased;

		for ( int station = 1; station <= 3; station++)
		{
			cout << "Enter the price per gallon at station #" << station << ": $";
			if (station == 1)
			{
				cin >> price1;
			}
			if (station == 2)
			{
				cin >> price2;
			}
			if (station == 3)
			{
				cin >> price3;
			}
		}

		avgPPG = (price1 + price2 + price3) / 3;
		OneMileTrip = avgPPG / avgMPG;
	
		cout << "\nYour car's average mile per gallon is: " << avgMPG << " mpg" << endl;
		cout << "You bought gas at an average $" << setprecision(2) << fixed << avgPPG << " per gallon\n";
		cout << "The cost for your car to go 1 mile is $" << setprecision(2) << fixed << OneMileTrip << endl;
		
		if (avgMPG > 0 && avgMPG <= 15)
		{
			cout << "Your car is very inefficient.\n\n\n";
		}
		if (avgMPG >= 16 && avgMPG <= 30)
		{
			cout << "Your car's efficiency is OK.\n\n\n";
		}
		if (avgMPG >= 31)
		{
			cout << "Your car is very efficient.\n\n\n";
		}
	}

	system ("pause");
	return 0;
}