/*
Marty Stepp, CSE 142, Autumn 2009
This program prompts the user for numbers until a given special
"sentinel" value is typed, then displays the sum of the numbers.

This is an example of a sentinel loop, which is also
an example of a fencepost problem.

Example output:
Enter a number (-1 to quit): 10
Enter a number (-1 to quit): 20
Enter a number (-1 to quit): 30
Enter a number (-1 to quit): -1
The sum is 60
*/

import java.util.*;   // for Scanner

public class SentinelSum {
    public static final int SENTINEL = -1;

    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        
        // read ints from scanner until we see a 0
        // any variable(s) used in your while loop test must be declared BEFORE the loop header
        int sum = 0;
        
        // fencepost loop; move one "post" out of the loop
        // "posts" - prompt/read an int
        // "wires" - add them to a cumulative sum
        System.out.print("Enter a number (" + SENTINEL + " to quit): ");
        int n = console.nextInt();

        while (n != SENTINEL) {
            sum += n;   // sum = sum + n;     sum *= n;  sum = sum * n;
            System.out.print("Enter a number (" + SENTINEL + " to quit): ");
            n = console.nextInt();
        }
        System.out.println("The sum is " + sum);
    }
}