Compilare: main.cpp: In function 'char solve(long long int, long long int, long long int)': main.cpp:18:11: 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] 18 | if (len == s.size()) { | ~~~~^~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:41:17: 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] 41 | for (i = 0; i < s.size(); i++) | ~~^~~~~~~~~~