Noble Integer

Description

You are given an integer array. Determine if an integer x exists such that the number of integers greater than x in the array is equal to x.

Let's consider the array [4, 5, 8, 3]. You can see that 4, 5 and 8 are greater than 3. So, the number of integers greater than 3 in the array is 3. Hence, you return 1.

Input Format:

The input contains the number of elements in the array, followed by the elements in the array.

Output Format:

The output returns 1 if such an integer x exists or returns -1 if such an integer x does not exist.

Sample Test Cases:

Input:

4 4 5 8 3

Output:

1

Input:

4 4 2 8 3

Output:

-1