combo.cpp: In function 'std::string guess_sequence(int)':
combo.cpp:38:21: error: could not convert '(((int)opc.std::__cxx11::basic_string<char>::operator[](0)) + ((int)opc.std::__cxx11::basic_string<char>::operator[](1)))' from 'int' to 'std::string' {aka 'std::__cxx11::basic_string<char>'}
38 | l1 = press(opc[0] + opc[1]) , l2 = press(opc[0] + opc[2]);
combo.cpp:38:51: error: could not convert '(((int)opc.std::__cxx11::basic_string<char>::operator[](0)) + ((int)opc.std::__cxx11::basic_string<char>::operator[](2)))' from 'int' to 'std::string' {aka 'std::__cxx11::basic_string<char>'}
38 | l1 = press(opc[0] + opc[1]) , l2 = press(opc[0] + opc[2]);