Compilare: user.cpp: In function ‘int main()’: user.cpp:20:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();++i) ^ user.cpp:25:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();++i) ^ user.cpp:55:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<polo.size();++i) ^ user.cpp:57:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<polo.size();++i) ^ user.cpp:76:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<polo.size();++i) ^