plz, help me! why i get crash(access violation).
// LCA (least common ancestor) offline by using interval tree in O(logN)
// Solution by Serekov Abzal

#pragma comment(linker, "/STACK:16777216")

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <queue>

using namespace std;
int ADD = 65536;
int inf = 9999999;
vector <vector <pair<int, int> > > graph;
vector <bool> b(50001, false);
vector <int> h(50001, 0);
vector <int> order;
vector <int> d(50001, 0);
vector <int> first(50001, -1);
pair <int, int> tree[2 * 65536 + 1];
int n, root = 0;
void init_graph()
{
    scanf("%d", &n);
    graph.resize(n);
    for (int i = 0; i < n - 1; i++)
    {
        int u, v, w;
        scanf("%d%d%d", &u, &v, &w);
        graph[u].push_back(make_pair(v, w));
        graph[v].push_back(make_pair(u, w));
    }
};
void dfs(int v, int p)
{
    b[v] = true;
    h[v] = p;
    order.push_back(v);
    for (int i = 0; i < graph[v].size(); i++)
        if (!b[graph[v][i].first])
        {
            dfs(graph[v][i].first, p + 1);
            order.push_back(v);
        }
};
void bfs(int v)
{
    queue <int> Q;
    Q.push(v);
    while (!Q.empty())
    {
        int u = Q.front();
        b[u] = true;
        for (int i = 0; i < graph[u].size(); i++)
            if (!b[graph[u][i].first])
            {
                d[graph[u][i].first] = d[u] + graph[u][i].second;
                Q.push(graph[u][i].first);
            }
        Q.pop();
    }
};
void prepare()
{
    h[root] = 0;
    dfs(root, 0);
    for (int i = 0; i < order.size(); i++)
        if (first[order[i]] == -1)
            first[order[i]] = i;
    for (int i = 0; i < n; i++) b[i] = false;
    d[root] = 0;
    bfs(root);
};
int minimum(int u, int v)
{
    int l = u, r = v, ans = inf, ver = inf;
    while (l <= r)
    {
        if (l % 2 == 1)
        {
            if (tree[l].second < ans)
            {
                ans = tree[l].second;
                ver = tree[l].first;
            }
            l++;
        };
        if (r % 2 == 0)
        {
            if (tree[r].second < ans)
            {
                ans = tree[r].second;
                ver = tree[r].first;
            }
            --r;
        }
        l/=2; r/=2;
    }
    return ver;
};
int lca(int u, int v)
{
    int l = first[u] + ADD, r = first[v] + ADD;
    return minimum(l, r);
};
void init_zaprosi()
{
    int m;
    scanf("%d", &m);
    for (int i = 0; i < m; i++)
    {
        int u, v;
        scanf("%d%d", &u, &v);
        int ans = d[u] + d[v] - 2 * d[lca(u, v)];
        printf("%d\n", ans);
    }
};
void tree_build()
{
    for (int i = 0; i <= 2 * ADD; i++)
    tree[i] = make_pair(-1, inf);

    for (int i = ADD; i < ADD + order.size(); i++)
    {
        tree[i].first = order[i - ADD];
        tree[i].second = h[order[i - ADD]];
    }
    for (int i = ADD - 1; i > 0; i--)
    {
        if (tree[2 * i].first == -1 || tree[2 * i + 1].first == -1)
        {
            if (!(tree[2 * i].first == -1 && tree[2 * i + 1].first == -1))
            {
                if (tree[2 * i].first == -1) tree[i] = tree[2 * i + 1]; else tree[i] = tree[2 * i];
            }
        }
        else
        {
            if (tree[2 * i].second < tree[2 * i + 1].second) tree[i] = tree[2 * i];    else tree[i] = tree[2 * i + 1];
        }
    }
};
int main()
{
    init_graph();
    prepare();
    tree_build();
    init_zaprosi();
    return 0;
}