Compilare: user.cpp: In function ‘int main()’: user.cpp:20:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.size();i++) ^ user.cpp:30:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<ss.size();i++) ^ user.cpp:48:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.size();i++) ^