Compilare: user.cpp: In function ‘void euler(int)’: user.cpp:15:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<G[x].size();++i) ^ user.cpp: In function ‘int main()’: user.cpp:53:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<G[y].size();++i) ^