## Goal

A restaurant sells portions of chicken nuggets in boxes. As a tricky client you want to puzzle the waiter by asking the impossible : find the highest number of nuggets that they cannot serve you.

For example, if the restaurant sells boxes of 2 or 5 portions of nuggets, the waiter cannot serve you 1 or 3 portions but they can serve you every other quantity, so the answer should be 3.

If the restaurant sells boxes of 6 or 8 portions however, the waiter cannot serve you any odd number of portions and there is no maximum (=Infinity), so the answer should be -1.
Input

**Line 1 :** The number `N` of boxes the restaurant serves.

`N` lines : The number `P` of nuggets in each box.

Output

The maximal number of nuggets that is impossible to get, -1 if there is no maximum (=Infinity).

Constraints

1<`N`<20

2<`P`<2000