题目描述
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.
Examples
Input
2 4
0 3
Output
7
Input
2 4
0 5
Output
8
Input
4 1000000000
0 1000 1000000 1000000000
Output
2000000000
Input
1 1
0
Output
1
Input
9 10
0 3 5 7 100 110 200 300 311
Output
67
输入格式
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输出格式
见题面