combo.cpp: In function 'std::string guess_sequence(int)':
combo.cpp:17:18: warning: comparison of integer expressions of different signedness: 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
17 | while(res.size()<=N-2){
| ~~~~~~~~~~^~~~~
combo.cpp:19:8: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
19 | if(op==res.size()){
| ~~^~~~~~~~~~~~
combo.cpp:21:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
21 | }else if(op==res.size()+1){
| ~~^~~~~~~~~~~~~~
combo.cpp:23:9: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
23 | if(op==res.size()) res=res+c[0]+c[2];
| ~~^~~~~~~~~~~~
combo.cpp:24:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
24 | else if(op==res.size()+1) res=res+c[1]+c[1];
| ~~^~~~~~~~~~~~~~
combo.cpp:28:9: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
28 | if(op==res.size()) res=res+c[1]+c[0];
| ~~^~~~~~~~~~~~
combo.cpp:29:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
29 | else if(op==res.size()+1) res=res+c[0]+c[0];
| ~~^~~~~~~~~~~~~~
combo.cpp:33:18: warning: comparison of integer expressions of different signedness: 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
33 | while(res.size()!=N){
| ~~~~~~~~~~^~~
combo.cpp:34:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
34 | if(press(res+c[0])==res.size()+1) res=res+c[0];
| ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
combo.cpp:35:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
35 | else if(press(res+c[1])==res.size()+1) res=res+c[1];
| ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~