Compilare: main.cpp: In function 'std::string postfix(std::string)': main.cpp:28:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 28 | for(int i=0; i<e.size(); i++) | ~^~~~~~~~~ main.cpp: In function 'long long int ToNum(std::string)': main.cpp:80:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 80 | for(int i=0;i<s.size();i++) | ~^~~~~~~~~ main.cpp: In function 'int main()': main.cpp:106:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 106 | for(int i=0;i<e.size();i++) | ~^~~~~~~~~