Compilare: user.cpp: In function ‘void erase(int, int)’: user.cpp:28:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<N[x].size();i++) ^ user.cpp: In function ‘void go()’: user.cpp:43:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<sol.size();i++) ^ user.cpp:49:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int p=0;p<N[i].size();p++) { ^