Compilare: user.cpp: In function ‘void euler(int)’: user.cpp:25:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(Sol.size()<N) ^ user.cpp: In function ‘int main()’: user.cpp:51:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<Sol.size();++i) g<<Sol[i].first<<' '<<Sol[i].second<<'\n'; ^