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A - Double Click

Score : $100$ points

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.

4 500
300 900 1300 1700

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.

5 99
100 200 300 400 500

-1

No double click was fired, so print -1.

4 500
100 600 1100 1600

600

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