comefrom: <qiyuangong>294_Flip_Game_II_2.py
code: def firstMissingNumber(lut):
      ls = len(lut)
      for i in range(ls):
          if i not in lut:
              return i
      return ls
masked: def sample_funcname ( var_0 ) :
      var_2 = len ( var_0 )
      for var_4 in range ( var_2 ) :
          if var_4 not in var_0 :
              return var_4
      return var_2
  