Compilare: main.cpp: In function 'int main()': main.cpp:81:26: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 81 | for(int i = 0; i < s.size(); i++) { | ~~^~~~~~~~~~ main.cpp:83:99: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 83 | if( (s[i] == '+' || s[i] == '*') && (s[i - 1] == '+' || s[i - 1] == '*' || (i + 1 != s.size() && s[i + 1] == ')') || s[i - 1] == '(') ) { | ~~~~~~^~~~~~~~~~~