output_description: Print the answer.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      s_{1}s_{2}s_{3}
attempt: sss = input()
  print(sss.count("1"))
  
problem_description: Statement
  
  Snuke has a grid consisting of three squares numbered 1, 2 and 3. In each
  square, either `0` or `1` is written. The number written in Square i is s_i.
  
  Snuke will place a marble on each square that says `1`. Find the number of
  squares on which Snuke will place a marble.
samples: [{"input": "101", "output": "2\n    \n\n  * A marble will be placed on Square 1 and 3.\n\n* * *"}, {"input": "000", "output": "0\n    \n\n  * No marble will be placed on any square."}]