cheesecake is participating in a push-up contest with ~N~ of his friends.

Each participant does a unique number of push-ups between ~1~ and ~N~. However, cheesecake was too busy organizing DMPG and unfortunately forgot how many push-ups he did!

As cheesecake is worried about whether or not bobhob314, with his wonderfully toned figure and boyish charm, won the contest, help him figure out how many push-ups he did, given the number of push-ups done by the other participants.

Input Specification

The first line of input will consist of ~1~ integer, ~N~ ~(1 \le N \le 10^5)~.
The next ~N-1~ lines will consist of the number of push-ups that each of cheesecake's friends did.

Output Specification

The number of push-ups that cheesecake did.

Sample Input

5
1
2
3
5

Sample Output

4