Compilare: main.cpp: In function 'int main()': main.cpp:15:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 15 | for(int i=0;i<a.size();i++) | ~^~~~~~~~~ main.cpp:21:18: 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(int i=1;i<a.size();i++) | ~^~~~~~~~~ main.cpp:40:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 40 | if((x+1)*2<=a.size()&&ff[x]) | ~~~~~~~^~~~~~~~~~