Compilare: main.cpp: In function 'int main()': main.cpp:86:13: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 86 | while (i<s.size()) { | ~^~~~~~~~~ main.cpp:93:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 93 | while (i<s.size() && s[i] >= '0' && s[i] <= '9') { | ~^~~~~~~~~ main.cpp:124:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 124 | if(i < s.size() && s[i] != '(' && s[i] != ')') { | ~~^~~~~~~~~~