a reference of type "std::string &" (not const-qualified) cannot be initialized with a value of type "const char [4]"
a reference of type "std::string &" (not const-qualified) cannot be initialized with a value of type "const char [4]"
a reference of type "std::string &" (not const-qualified) cannot be initialized with a value of type "const char [4]"
a reference of type "std::string &" (not const-qualified) cannot be initialized with a value of type "const char [4]"