Last Occurrence Position

Source: Phước Hưng OJ

Version: Phuoc Hung OJ Extended

Problem Statement

Given a target x and n integers, output the last 1-based position containing x. If x never occurs, or n=0, output -1. Process values as a stream.

Input

The first line contains n and x (0<=n<=100000; x is a signed 32-bit integer). Exactly n signed 32-bit integers follow.

Output

Print the last 1-based position, or -1 if absent.

Subtasks

• Subtask 1 (20%): $n\le5,|x|,|a_i|\le10$.
• Subtask 2 (30%): $n\le500,|x|,|a_i|\le10^4$.
• Subtask 3 (50%): $n\le100000$ và mọi giá trị thuộc miền int 32 bit.

Examples

Example 1

Input:

5 2
2 3 2 4 2

Output:

5

Explanation:

The target appears at positions 1, 3, and 5; the last is 5.

Example 2

Input:

0 -4

Output:

-1

Explanation:

No elements are present.