old_contents: #!/usr/bin/env python
  from __future__ import print_function, unicode_literals
  from os import chdir, getcwd, getenv
  from subprocess import call
  
  PYTHON = getenv('PYTHON', 'python')
  FC = getenv('FC', 'f95')
  DIR = getenv('DIR', './advent2015')
  
  puzzles = ['01', '02', '03']
  
  for puzzle in puzzles:
      print('Puzzle {}'.format(puzzle))
  
      py_src = './puzzle{}.py'.format(puzzle)
      f95_src = './puzzle{}.f95'.format(puzzle)
  
      py_cmd = [PYTHON, py_src]
      f95_cmd_1 = [FC, f95_src]
      f95_cmd_2 = ['./a.out']
  
      chdir(DIR)
      call(py_cmd)
      chdir('..')
      chdir('{}.f'.format(DIR))
      call(f95_cmd_1)
      call(f95_cmd_2)
      chdir('..')
      print('')
  
new_contents: #!/usr/bin/env python
  from __future__ import print_function, unicode_literals
  from os import chdir, getcwd, getenv
  from subprocess import call
  
  PYTHON = getenv('PYTHON', 'python')
  FC = getenv('FC', 'f95')
  DIR = getenv('DIR', './advent2015')
  
  puzzles = ['01', '02', '03', '04']
  
  for puzzle in puzzles:
      print('Puzzle {}'.format(puzzle))
  
      py_src = './puzzle{}.py'.format(puzzle)
      f95_src = './puzzle{}.f95'.format(puzzle)
  
      py_cmd = [PYTHON, py_src]
      f95_cmd_1 = [FC, f95_src]
      f95_cmd_2 = ['./a.out']
  
      chdir(DIR)
      call(py_cmd)
      chdir('..')
      chdir('{}.f'.format(DIR))
      call(f95_cmd_1)
      call(f95_cmd_2)
      chdir('..')
      print('')
  
subject: Add day 4