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:63:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(v[st[i]].size()==r) ^