Compilare: user.cpp: In function ‘int main()’: user.cpp:47:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=2; i<a.size(); ++i) { ~^~~~~~~~~ user.cpp:56:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<st.size(); ++i) cout<<setprecision(10)<<fixed<<st[i].first<<" "<<st[i].second<<"\n"; ~^~~~~~~~~~