eolymp
Competitions

XOR Contest

Lost card

For the board game the deck of cards is used with numbers from 1 to n (positive integer n does not exceed 106). One card is lost. Find it.

Input

The first number is n. Then goes n - 1 numbers of left cards.

Output

Print the number of lost card.

Time limit 2 seconds
Memory limit 128 MiB
Input example #1
5 1 2 3 4 
Output example #1
5
Input example #2
4 3 2 4
Output example #2
1