/*
 * C Program To Identify the Missing Number in an Integer
 * Array of Size N-1 with Numbers[1,N]
 */
#include <stdio.h>
#define MAX 15
int missing_number_array(int [],int);

int main()
{
    int a[MAX], num, i, n;
    printf("enter the range of array\n");
    scanf("%d", &n);
    for (i = 0; i < n; i++)
        {
            printf("enter a[%d]element into the array:", i);
            scanf("%d", &a[i]);
        }
    num = missing_number_array(a, n);
    printf("The missing number -> %d\n", num);
}

/* To find the missing number in array */
int missing_number_array(int a[],  int n)
{
    int i;
    int s1 = 0;
    int s2 = 0;
    for (i = 0; i < n; i++)
        s1 = s1 ^ a[i];
    for (i = 1; i <= n + 1; i++)
        s2 = s2 ^ i;
    return (s1 ^ s2);
}