Borderou de evaluare (job #541513)

Eroare de compilare: user.cpp: In function ‘int main()’: user.cpp:20:26: error: no matching function for call to ‘std::basic_string<char>::push_back(std::string&)’ user.cpp:20:26: note: candidate is: /usr/include/c++/4.6/bits/basic_string.h:1043:7: note: void std::basic_string<_CharT, _Traits, _Alloc>::push_back(_CharT) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>] /usr/include/c++/4.6/bits/basic_string.h:1043:7: note: no known conversion for argument 1 from ‘std::string {aka std::basic_string<char>}’ to ‘char’ user.cpp:26:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]