Score : $100$ points

问题描述

Takahashi 在时间 $0$ 开启了一台计算机，并在不同时间点击了鼠标共 $N$ 次。第 $i$ 次（$1 \le i \le N$）的点击发生在时间 $T_i$。

若他在时间 $x_1$ 和时间 $x_2$（其中 $x_1 < x_2$）连续点击鼠标，如果满足 $x_2 - x_1 \le D$，则称在时间 $x_2$ 发生了一次双击。

请问第一次双击发生的时间是什么？如果没有发生过双击，则输出 -1。

以上为通义千问 qwen-max 翻译，仅供参考。

Problem Statement

Takahashi turned on a computer at time $0$ and clicked the mouse $N$ times. The $i$-th $(1 \le i \le N)$ click was at time $T_i$.

If he consecutively clicked the mouse at time $x_1$ and time $x_2$ (where $x_1 < x_2$), a double click is said to be fired at time $x_2$ if and only if $x_2 - x_1 \le D$.

What time was a double click fired for the first time? If no double click was fired, print -1 instead.

Constraints

• $1 \le N \le 100$
• $1 \le D \le 10^9$
• $1 \le T_i \le 10^9(1 \le i \le N)$
• $T_i < T_{i+1}(1 \le i \le N-1)$
• All values in the input are integers.

Input

The input is given from Standard Input in the following format:

$N$ $D$

$T_1$ $T_2$ $\dots$ $T_N$

Output

If at least one double click was fired, print the time of the first such event; otherwise, print -1.

Sample Input 1

4 500
300 900 1300 1700

Sample Output 1

1300

Takahashi clicked the mouse at time $900$ and $1300$. Since $1300 - 900 \le 500$, a double click was fired at time $1300$.

A double click had not been fired before time $1300$, so $1300$ should be printed.

Sample Input 2

5 99
100 200 300 400 500

Sample Output 2

-1

No double click was fired, so print -1.

Sample Input 3

4 500
100 600 1100 1600

Sample Output 3

600

If multiple double clicks were fired, be sure to print only the first such event.

update @ 2024/3/10 12:19:41