Problem Statement

We have $N$ bricks arranged in a row from left to right.

The $i$-th brick from the left $(1 \leq i \leq N)$ has an integer $a_i$ written on it.

Among them, you can break at most $N-1$ bricks of your choice.

Let us say there are $K$ bricks remaining. Snuke will be satisfied if, for each integer $i$ $(1 \leq i \leq K)$, the $i$-th of those brick from the left has the integer $i$ written on it.

Find the minimum number of bricks you need to break to satisfy Snuke's desire. If his desire is unsatisfiable, print -1 instead.

Constraints

• All values in input are integers.
• $1 \leq N \leq 200000$
• $1 \leq a_i \leq N$

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 ... a_N

Output

Print the minimum number of bricks that need to be broken to satisfy Snuke's desire, or print -1 if his desire is unsatisfiable.