Compilare: user.cpp: In function ‘bool pairup(int)’: user.cpp:14:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int it=0;it<l[x].size();it++) ^ user.cpp:21:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int it=0;it<l[x].size();it++) ^ user.cpp: In function ‘int main()’: user.cpp:43:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(v[i].size()==r) ^ user.cpp:47:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(v[v[i][j]].size()==r-1||v[i][j]<i) ^