There is a sequence of n numbers. And in this sequence, there is only one number appears twice.
Can you tell me which number appears twice.

There are multiple test cases in the input file.
In each case the first line contains an integer n (2<=n<=1000) — the size of the sequence.
The second line contains n integers a1, a2, ..., an (1<=ai<=1000) — the elements of the sequence.

For each case print a single line with the number.