Problem Statement

In a public bath, there is a shower which emits water for $T$ seconds when the switch is pushed.

If the switch is pushed when the shower is already emitting water, from that moment it will be emitting water for $T$ seconds. Note that it does not mean that the shower emits water for $T$ additional seconds.

$N$ people will push the switch while passing by the shower. The $i$-th person will push the switch $t_i$ seconds after the first person pushes it.

How long will the shower emit water in total?

Constraints

• $1 ≤ N ≤ 200,000$
• $1 ≤ T ≤ 10^9$
• $0 = t_1 < t_2 < t_3 < , ..., < t_{N-1} < t_N ≤ 10^9$
• $T$ and each $t_i$ are integers.

Input

Input is given from Standard Input in the following format:

N T
t_1 t_2 ... t_N

Output

Assume that the shower will emit water for a total of $X$ seconds. Print $X$.