output_description: Assume that the shower will emit water for a total of X seconds. Print X.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N T
      t_1 t_2 ... t_N
attempt: n, t = list(input())
  ts = list(input())
  print(sum([min(t, next - prev) for prev, next in zip(ts, ts[1:])], t))
  
problem_description: 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?
samples: [{"input": "2 4\n    0 3", "output": "7\n    \n\nThree seconds after the first person pushes the water, the switch is pushed\nagain and the shower emits water for four more seconds, for a total of seven\nseconds.\n\n* * *"}, {"input": "2 4\n    0 5", "output": "8\n    \n\nOne second after the shower stops emission of water triggered by the first\nperson, the switch is pushed again.\n\n* * *"}, {"input": "4 1000000000\n    0 1000 1000000 1000000000", "output": "2000000000\n    \n\n* * *"}, {"input": "1 1\n    0", "output": "1\n    \n\n* * *"}, {"input": "9 10\n    0 3 5 7 100 110 200 300 311", "output": "67"}]