A non-empty zero-indexed array A consisting of N integers is given. The

*first covering prefix*of array A is the smallest integer P such that 0≤PFor example, the first covering prefix of the following 5−element array A:

A[0] = 2 A[1] = 2 A[2] = 1 A[3] = 0 A[4] = 1

is 3, because sequence [ A[0], A[1], A[2], A[3] ] equal to [2, 2, 1, 0], contains all values that occur in array A.

Write a function

`class Solution { public int ps(int[] A); }`

that, given a zero-indexed non-empty array A consisting of N integers, returns the first covering prefix of A.

Assume that:

For example, given array A such that

- N is an integer within the range [1..1,000,000];
- each element of array A is an integer within the range [0..N−1].

A[0] = 2 A[1] = 2 A[2] = 1 A[3] = 0 A[4] = 1

the function should return 3, as explained above.

Complexity:

- expected worst-case time complexity is O(N);
- expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments).

**Solution:**import java.util.HashSet; import java.util.Set; class Solution { public int ps ( int[] A ) { Set set = new HashSet(); int index =-1; for(int i=0;i