#include "assert.h"
#include "stdio.h"
#include <string.h>

/* Writes the sum of the array a of length n of integers
 * into sum.  Return 0 if successful and -1 if either of a
 * or sum is NULL or n < 0.
 */
int sum(int * a, int n, int * sum) {
  if (!a || n < 0 || !sum)
    return -1;

  *sum = 0;
  while (n > 0) {
    *sum += *a;
    a++;
    n--;
  }
  return 0;
}

#define MAX_N 100

int main() {
  int numbers[MAX_N];
  int num, s, err, ret;
  int i = 0;

  while (1) {
    // check if out of space
    if (i == MAX_N) {
      printf("Too many numbers.\n");
      return -1;
    }
    // read an integer
    ret = scanf("%d", &num);
    // check if stdin has closed
    if (ret == EOF)
      // stdin has closed, so exit the loop
      break;
    // check if scanf returned 0, indicating bad input
    if (ret == 0) {
      printf("Expected an integer.\n");
      return -1;
    }
    // add the input to the array
    numbers[i] = num;
    i++;
  }
  // compute the sum
  err = sum(numbers, i, &s);
  assert (!err);

  printf("Sum: %d\n", s);
  return 0;
}