Compilare: user.cpp: In function ‘int cost(std::string, std::string)’: user.cpp:27:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<a.size();i++) ^ user.cpp:29:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=0;j<b.size();j++) ^ user.cpp: In function ‘int main()’: user.cpp:58:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=i+1;j<S.size();j++) ^