Odd Gnome

Source: Kattis

Version: Phuoc Hung OJ Extended

Problem

A lineup contains IDs $g_1,\ldots,g_n$. Exactly one position $p$, $2\le p\le n-1$, breaks the consecutive-increasing rule. It is the first position satisfying $g_p\ne g_{p-1}+1$. Output this 1-based position. The PHOJ adaptation uses one gnome group per input file.

Input

The first line contains $n$. The second line contains the $n$ IDs.

Output

Print the 1-based anomalous position.

Subtask

Subtask 1 (20 points): $3\le n\le10$.

Subtask 2 (30 points): $3\le n\le100$.

Subtask 3 (50 points): $3\le n\le1000$.

Example

Input

7
10 11 12 99 13 14 15

Output

4

Explanation

$g_4=99$ is the first value that is not one larger than its predecessor.