/* Sentinel controlled loop - Add numbers entered by user. Stop when meeting SENTINEL - OK */

#include <stdio.h>
#define SENTINEL -1

int main(void) {
  int sum, number;

  /* Initialization */
  sum = 0;

  /* Get first number */
  printf("Enter number (-1 terminates): ");
  scanf("%d", &number);

  while (number != SENTINEL){
    /* Add number to sum */
    sum += number;
    
    /* Get next number */
    printf("Enter number (-1 terminates): ");
    scanf("%d", &number);
  }

  /* Report the output */
  printf("The sum is %d\n", 
         sum);

  return 0;
}