/* EXPECTED OUTPUT:
Type a number (-1 to quit): 10
Type a number (-1 to quit): 20
Type a number (-1 to quit): 30
Type a number (-1 to quit): 40
Type a number (-1 to quit): -1
Sum = 100

*/

// This program demonstrates an error in our output that is caused
// by a fencepost problem.
// Can you see the error?  How can we fix it?
// (Corrected version is below in comments)
public class CumulativeSum {
    // incorrect version
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        int sum = 0;
        int number = 0;
        
        while (number != -1) {
            System.out.print("Type a number (-1 to quit): ");
            number = console.nextInt();
            sum += number;
        }
        
        System.out.println("Sum = " + sum);
    }
    
    /* correct version:
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        int sum = 0;
        System.out.print("Type a number (-1 to quit): ");
        int number = console.nextInt();
        
        while (number != -1) {
            sum += number;
            System.out.print("Type a number (-1 to quit): ");
            number = console.nextInt();
        }
        
        System.out.println("Sum = " + sum);
    }
    */
}