Compilare: user.cpp: In function ‘int main()’: user.cpp:44:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=i+(i&1); j<v.size(); j+=2) fout << v[j].first << ' ' << v[j].second << ' '; fout << '\n'; ^ user.cpp:45:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=i+1-(i&1); j<v.size(); j+=2) fout << v[j].first << ' ' << v[j].second << ' '; fout << '\n'; ^