output_description: Print the minimum number of stones that needs to be recolored.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      S
attempt: print(sum(map(len, input().split("#")[1:])))
  
problem_description: Statement
  
  There are N stones arranged in a row. Every stone is painted white or black. A
  string S represents the color of the stones. The i-th stone from the left is
  white if the i-th character of S is `.`, and the stone is black if the
  character is `#`.
  
  Takahashi wants to change the colors of some stones to black or white so that
  there will be no white stone immediately to the right of a black stone. Find
  the minimum number of stones that needs to be recolored.
samples: [{"input": "3\n    #.#", "output": "1\n    \n\nIt is enough to change the color of the first stone to white.\n\n* * *"}, {"input": "5\n    #.##.", "output": "2\n    \n\n* * *"}, {"input": "9\n    .........", "output": "0"}]