代码：

#include <iostream>
#include <vector>
#include <queue>
#include <cmath>

using namespace std;

const int MAXN = 1e5 + 5;
const int MAXLOG = 20;

vector<int> adj[MAXN];
int parent[MAXN], depth[MAXN];
int up[MAXLOG + 1][MAXN];

void bfs(int root) {
    queue<int> q;
    q.push(root);
    parent[root] = 0;
    depth[root] = 0;
    while (!q.empty()) {
        int u = q.front();
        q.pop();
        for (int v : adj[u]) {
            if (v != parent[u]) {
                parent[v] = u;
                depth[v] = depth[u] + 1;
                q.push(v);
            }
        }
    }
}

void preprocess(int n) {
    for (int u = 1; u <= n; ++u) {
        up[0][u] = parent[u];
    }
    for (int k = 1; k <= MAXLOG; ++k) {
        for (int u = 1; u <= n; ++u) {
            up[k][u] = up[k - 1][up[k - 1][u]];
        }
    }
}

int lca(int x, int y) {
    if (depth[x] < depth[y]) {
        swap(x, y);
    }
    int diff = depth[x] - depth[y];
    for (int k = MAXLOG; k >= 0; --k) {
        if (diff & (1 << k)) {
            x = up[k][x];
        }
    }
    if (x == y) {
        return x;
    }
    for (int k = MAXLOG; k >= 0; --k) {
        if (up[k][x] != up[k][y]) {
            x = up[k][x];
            y = up[k][y];
        }
    }
    return up[0][x];
}

int distance(int x, int y) {
    int lca_node = lca(x, y);
    return depth[x] + depth[y] - 2 * depth[lca_node];
}

int main() {
    int n;
    cin >> n;
    for (int i = 0; i < n - 1; ++i) {
        int x, y;
        cin >> x >> y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    bfs(1);
    preprocess(n);
    int Q;
    cin >> Q;
    for (int i = 0; i < Q; ++i) {
        int x, y;
        cin >> x >> y;
        cout << distance(x, y) << endl;
    }
    return 0;
}