combo.cpp: In function 'std::string guess_sequence(int)':
combo.cpp:9:13: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
9 | for (a=0; a<st.length(); a++)
| ~^~~~~~~~~~~~
combo.cpp:16:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
16 | for (b=0; b<st.length(); b++)
| ~^~~~~~~~~~~~
combo.cpp:21:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
21 | for (c=0; c<st.length(); c++)
| ~^~~~~~~~~~~~
combo.cpp:31:1: warning: control reaches end of non-void function [-Wreturn-type]
31 | }
| ^