Compilare: main.cpp: In function 'int main()': main.cpp:19:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 19 | for(i=0; i<s.size()-1; i++) | ~^~~~~~~~~~~ main.cpp:11:9: warning: unused variable 'n' [-Wunused-variable] 11 | int n,op,imp,t,i; | ^