Compilare: user.cpp: In function ‘void euler()’: user.cpp:23:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<v[y].size(); i++) if(v[y][i] == x) { v[y][i] = v[y][v[y].size()-1]; v[y].pop_back(); break; } ^ user.cpp: In function ‘int main()’: user.cpp:49:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<sol.size(); i++) g<<sol[i]<<" "; ^