Compilare: user.cpp: In function ‘void df(int, int)’: user.cpp:45:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int it=0;it<a[k].size();++it) ^ user.cpp: In function ‘int main()’: user.cpp:83:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<sol.size();++i) ^ user.cpp:85:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<sol[i].size();++j) ^