#include <iostream>
#include <vector>

using namespace std;

vector <vector<int>> graf;
vector<int> height, order, pos, tree;
vector<bool> used;

void dfs(int v, int h)
{
    used[v] = true;
    height[v] = h;
    order.push_back(v);
    for (int i = 0; i != graf[v].size(); i++) {
        if (!used[graf[v][i]])
        {
            dfs(graf[v][i], h + 1);
            order.push_back(v);
        }
    }
}

void createTree(int i, int l, int r)
{
    if (l == r) {
        tree[i] = order[l];
    }
    else{
        int m = (l + r) / 2;//
        createTree(i + i, l, m);
        createTree(i + i + 1, m + 1, r);
        tree[i] = height[tree[i + i]] < height[tree[i + i + 1]] ? tree[i + i] : tree[i + i + 1];
    }
}

int min(int i, int sl, int sr, int l, int r)
{
    if (sl == l && sr == r) {
        return tree[i];
    }
    int sm = (sl + sr) >> 1;
    if (r <= sm) {
        return min(i + i, sl, sm, l, r);
    }
    if (l > sm) {
        return min(i + i + 1, sm + 1, sr, l, r);
    }
    int ans1 = min(i + i, sl, sm, l, sm);
    int ans2 = min(i + i + 1, sm + 1, sr, sm + 1, r);
    return height[ans1] < height[ans2] ? ans1 : ans2;
}

int main()
{
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    int n;
    cin >> n;
    graf.resize(n);
    int a, b;
    for (int i = 0; i < n - 1; i++) {
        cin >> a;
        cin >> b;
        graf[a - 1].push_back(b - 1);
        graf[b - 1].push_back(a - 1);
    }

    height.resize(n);//
    used.resize(n);
    dfs(0, 1);
    tree.assign(order.size() * 4 + 1, -1);
    createTree(1, 0, order.size() - 1);
    pos.assign(n, -1);
    for (int i = 0; i < order.size(); ++i)
    {
        if (pos[order[i]] == -1) {
            pos[order[i]] = i;
        }
    }

        cin >> a;
        cin >> b;
        while (a != -1) {
            int left = pos[a - 1],
                right = pos[b - 1];
            if (left > right) { swap(left, right); }
            cout << min(1, 0, order.size() - 1, left, right) + 1 << endl;
            a = -1;
            cin >> a;
            cin >> b;
        }
}