/*
 * C Program to identify missing numbers in a given array
 */
#include <stdio.h>

void main()
{
    int n, i, j, c, t, b;
    printf("Enter size of array : ");
    scanf("%d", &n);
    int array[n - 1];     /* array size-1 */
    printf("Enter elements into array : \n");
    for (i = 0; i < n - 1; i++)
        scanf("%d", &array[i]);
    b = array[0];
    for (i = 1; i < n - 1; i++)
        b = b ^ array[i];
    for (i = 2, c = 1; i <= n; i++)
        c = c ^ i;
    c = c ^ b;
    printf("Missing element is : %d \n", c);
}

/*
Enter size of array : 6
Enter elements into array :
1
2
3
5
6
Missing element is : 4