Score : $300$ points
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?
Input is given from Standard Input in the following format:
$N$ $T$ $t_1$ $t_2$ ... $t_N$
Assume that the shower will emit water for a total of $X$ seconds. Print $X$.
2 4 0 3
Three seconds after the first person pushes the water, the switch is pushed again and the shower emits water for four more seconds, for a total of seven seconds.
2 4 0 5
One second after the shower stops emission of water triggered by the first person, the switch is pushed again.
4 1000000000 0 1000 1000000 1000000000
1 1 0
9 10 0 3 5 7 100 110 200 300 311