View Compilation Error

123981_0_13022.cpp
123981_0_13022.cpp(23) : error C2039: 'push_back' : is not a member of 'basic_string<char,struct std::char_traits<char>,class std::allocator<char> >'
123981_0_13022.cpp(47) : warning C4508: 'main' : function should return a value; 'void' return type assumed