/in/foo.cc: In function 'int main()':
/in/foo.cc:11:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < In.size(); i++)
                 ~~^~~~~~~~~~~
/in/foo.cc:15:15: error: invalid use of member function 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type = long unsigned int]' (did you forget the '()' ?)
    if(i == In.size - 1 && In[i] = 'X')
            ~~~^~~~