// A / b = C ... r, A >= 0, b > 0
vector<int>div(vector<int>&A,int b,int&r){
vector<int> C;
r =0;for(int i = A.size()-1; i >=0; i --){
r = r *10+ A[i];
C.push_back(r / b);
r %= b;}reverse(C.begin(), C.end());while(C.size()>1&& C.back()==0) C.pop_back();return C;}