Problem:
LCA: Lowest Common Ancestor

For a rooted tree, find the lowest common ancestor of two nodes u and v.

The given tree consists of n nodes and every node has a unique ID from 0 to n-1 where 0 is the root.

Input

n
k0 c1 c2 ... ck0
k1 c1 c2 ... ck1
:
kn-1 c1 c2 ... ckn-1
q
u1 v1
u2 v2
:
uq vq

The first line of the input includes an integer n, the number of nodes of the tree.

In the next n lines, the information of node i is given. ki is the number of children of node i, and c1, ... cki are node IDs of 1st, ... kth child of node i.

In the next line, the number of queryies q is given. In the next q lines, pairs of u and v are given as the queries.

Output

For each query, print the LCA of u and v in a line.

Constraints

1 ≤ n ≤ 100000

1 ≤ q ≤ 100000

Sample Input 1

8
3 1 2 3
2 4 5
0
0
0
2 6 7
0
0
4
4 6
4 7
4 3
5 2

Sample Output 1

1
1
0
0

Solution in C++14 (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rrep(i,n) for(int (i)=((n)-1);(i)>=0;(i)--)
#define itn int
#define miele(v) min_element(v.begin(), v.end())
#define maele(v) max_element(v.begin(), v.end())
#define SUM(v) accumulate(v.begin(), v.end(), 0LL)
#define lb(a, key) lower_bound(a.begin(),a.end(),key)
#define ub(a, key) upper_bound(a.begin(),a.end(),key)
#define COUNT(a, key) count(a.begin(), a.end(), key) 
#define BITCOUNT(x) __builtin_popcount(x)
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
using P = pair <int,int>;
using WeightedGraph = vector<vector <P>>;
using UnWeightedGraph = vector<vector<int>>;
using Real = long double;
using Point = complex<Real>; //Point and Vector2d is the same!
using Vector2d = complex<Real>;
const long long INF = 1LL << 60;
const int MOD = 1000000007;
const double EPS = 1e-15;
const double PI=3.14159265358979323846;
template <typename T> 
int getIndexOfLowerBound(vector <T> &v, T x){
    return lower_bound(v.begin(),v.end(),x)-v.begin();
}
template <typename T> 
int getIndexOfUpperBound(vector <T> &v, T x){
    return upper_bound(v.begin(),v.end(),x)-v.begin();
}
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
#define DUMPOUT cerr
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
istream &operator>>(istream &is, Point &p) {
    Real a, b; is >> a >> b; p = Point(a, b); return is;
}
template <typename T, typename U>
istream &operator>>(istream &is, pair<T,U> &p_var) {
    is >> p_var.first >> p_var.second;
    return is;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &vec) {
    for (T &x : vec) is >> x;
    return is;
}
template <typename T>
istream &operator>>(istream &is, vector<vector<T>> &df) {
    for(int i=0;i<df.size();i++)for(int j=0;j<df[i].size();j++)
    is >> df[i][j];
    return is;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var) {
    DUMPOUT<<'{';
    os << pair_var.first;
    DUMPOUT<<',';
    os << " "<< pair_var.second;
    DUMPOUT<<'}';
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, vector<T> &vec) {
    DUMPOUT<<'[';
    for (int i = 0; i < vec.size(); i++) 
    os << vec[i] << (i + 1 == vec.size() ? "" : " ");
    DUMPOUT<<']';
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, vector<vector<T>> &df) {
  for (auto& vec : df) os<<vec;
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var) {
    DUMPOUT << "{";
    repi(itr, map_var) {
        os << *itr;
        itr++;
        if (itr != map_var.end()) DUMPOUT << ", ";
        itr--;
    }
    DUMPOUT << "}";
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, set<T> &set_var) {
    DUMPOUT << "{";
    repi(itr, set_var) {
        os << *itr;
        itr++;
        if (itr != set_var.end()) DUMPOUT << ", ";
        itr--;
    }
    DUMPOUT << "}";
    return os;
}
void print() {cout << endl;}
template <class Head, class... Tail>
void print(Head&& head, Tail&&... tail) {
  cout << head;
  if (sizeof...(tail) != 0) cout << " ";
  print(forward<Tail>(tail)...);
}
void dump_func() {DUMPOUT << '#'<<endl;}
template <typename Head, typename... Tail>
void dump_func(Head &&head, Tail &&... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) > 0) DUMPOUT << ", ";
    dump_func(std::move(tail)...);
}
#ifdef DEBUG_
#define DEB
#define dump(...)                                                              \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                            \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]"        \
            << endl                                                            \
            << "    ",                                                         \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif

template <typename T>
struct doubling{
    int sz;
    vector <vector <T>> parents;
    vector <int> dep;
    doubling(UnWeightedGraph &g){
        sz = g.size();
        parents.resize(20), dep.resize(sz);
        rep(i, 20) parents[i].resize(sz);
        queue <tuple <int,int,int>> q;
        q.push(make_tuple(0, 0, 0)); //now, pre, depth
        while(!q.empty()){
            auto tmp = q.front(); q.pop();
            int now = get <0>(tmp), pre = get <1>(tmp), depth = get <2>(tmp);
            parents[0][now] = pre, dep[now] = depth;
            for(auto ne: g[now]) if(ne != pre) q.push(make_tuple(ne, now, depth+1));
        }
        for(int i=1;i<20;i++) rep(j, sz) parents[i][j] = parents[i-1][parents[i-1][j]];
    }
    /*doubling(WeightedGraph &g){
        sz = g.size();
        parents.resize(20), dep.resize(20);
        rep(i, 20) parents[i].resize(sz);
        queue <tuple <int,int,int>> q;
        q.push(make_tuple(0, 0, 0)); //now, pre, depth
        while(!q.empty()){
            auto tmp = q.front(); q.pop();
            int now = get <0>(tmp), pre = get <1>(tmp), depth = get <2>(tmp);
            parents[0][now] = pre, dep[now] = depth;
            for(auto ne: g[now]) if(ne.F != pre) q.push(make_tuple(ne.F, now, dep+1));
        }
        for(int i=1;i<20;i++) rep(j, sz) parents[i][j] = parents[i-1][parents[i-1][j]];
    }*/
    int getAncestor(int a, int k){
        int now = a;
        for(int i=19;i>=0;i--) if(k&(1<<i)) now = parents[i][now];
        return now;
    }
    int lca(int a, int b){
        if(a==b) return a;
        if(dep[a] > dep[b]) swap(a, b);
        for(int i=19;i>=0;i--) if(((dep[b] - dep[a]) >> i) & 1) b = parents[i][b];
        if(a==b) return a;
        for(int i=19;i>=0;i--) 
        if(parents[i][a] != parents[i][b]) a = parents[i][a], b = parents[i][b];
        return parents[0][a];
    }
    int dist(int a, int b){
        int anc = lca(a, b);
        return dep[a] + dep[b] - 2*dep[anc];
    }
    /*int query(int a, int b){
        int anc = lca(a, b);
        for(int i=19;i>=0;i--){
            if(dist&(1LL<<i)) {
                chmax(res, maxEdge[i][now]);
                now = parents[i][now];
            }
        }
        return res;
    }*/
};
int main(void) { cin.tie(0); ios::sync_with_stdio(false);
    int n; cin>>n;
    UnWeightedGraph g(n);
    rep(i, n){
        int k; cin>>k;
        rep(j, k){
            int a; cin>>a;
            g[i].emplace_back(a);
        }
    }
    int q; cin>>q;
    doubling<int> dou(g);
    while(q--){
        int a, b; cin>>a>>b;
        print(dou.lca(a, b));
    }
}