Problem Statement

You are given a sequence of length $N$ consisting of integers: $A=(A_1,\\ldots,A_N)$.

Find the smallest non-negative integer not in $(A_1,\\ldots,A_N)$.

Constraints

• $1 \\leq N \\leq 2000$
• $0 \\leq A_i \\leq 2000$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

$N$ $A_1$ $\\ldots$ $A_N$

Output

Print the answer.

Sample Input 1

8
0 3 2 6 2 1 0 0

Sample Output 1

4

The non-negative integers are $0,1,2,3,4,\\ldots$.
We have $0,1,2,3$ in $A$, but not $4$, so the answer is $4$.

Sample Input 2

3
2000 2000 2000

Sample Output 2

0