import java.text.DecimalFormat;
import java.util.Scanner;


public class mpg {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);
		DecimalFormat format = new DecimalFormat("###,###,##0.0");

		double init, fin, gal, mpg;
		System.out.println("Welcome to the Miles per Gallon Calculator!");

		init = 12;

		while (init >= 0){
			System.out.print("\nEnter the INITIAL ODOMETER READING or a negative number to STOP: ");
			init = scan.nextDouble();

			if(init >= 0){
				System.out.print("\nEnter the FINAL ODOMETER READING: ");
				fin = scan.nextDouble();
				System.out.print("\nEnter the number of GALLONS OF GAS used: ");
				gal = scan.nextDouble();

				mpg = (fin-init)/gal;
				System.out.print("\n\tMiles per Gallon: " +format.format(mpg) + "\n");
			}


		}
		System.out.println("\nBYE!!");

	}

}