output_description: If you can form at most x groups consisting of three or more students, print
  x.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
attempt: print(str(int(input()) // 3))
  
problem_description: Statement
  
  There are N students in a school.
  
  We will divide these students into some groups, and in each group they will
  discuss some themes.
  
  You think that groups consisting of two or less students cannot have an
  effective discussion, so you want to have as many groups consisting of three
  or more students as possible.
  
  Divide the students so that the number of groups consisting of three or more
  students is maximized.
samples: [{"input": "8", "output": "2\n    \n\nFor example, you can form a group of three students and another of five\nstudents.\n\n* * *"}, {"input": "2", "output": "0\n    \n\nSometimes you cannot form any group consisting of three or more students,\nregardless of how you divide the students.\n\n* * *"}, {"input": "9", "output": "3"}]