title: Divisibility By 7
signature: function divisibility_by_7(num)
source_py: def divisibility_by_7(num):
      if (num < 0):
          return divisibility_by_7((- num))
      if ((num == 0) or (num == 7)):
          return True
      if (num < 10):
          return False
      return divisibility_by_7(((num / 10) - (2 * (num - ((num / 10) * 10)))))
source_cpp: int divisibility_by_7(int num) {
    if ( num < 0 ) return divisibility_by_7 ( - num );
    if ( num == 0 || num == 7 ) return 1;
    if ( num < 10 ) return 0;
    return divisibility_by_7 ( num / 10 - 2 * ( num - num / 10 * 10 ) );
  }