Compilare: user.cpp: In constructor ‘Sir::Sir(const string&)’: user.cpp:28:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < s.size(); ++i) { ^ user.cpp: In function ‘int main()’: user.cpp:51:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = a.size() - 1; i < b.size(); ++i) { ^