#include <cstdio>
#include <vector>
using namespace std;
struct BIT {
    int n, t[2000010];
    void modify(int k, int x) {
        for (int i = k; i <= n; i += i & (-i)) {
            t[i] += x;
        }
    }
    int query(int k) {
        int ans = 0;
        for (int i = k; i >= 1; i -= i & (-i)) {
            ans += t[i];
        }
        return ans;
    }
} bt;
struct UnionSet {
    int n, fa[2000010];
    void init() {
        for (int i = 1; i <= n; i++) {
            fa[i] = i;
        }
    }
    int find(int x) {
        if (fa[x] == x) return x;
        return fa[x] = find(fa[x]);
    }
    void merge(int x, int y) {
        fa[find(x)] = find(y);
    }
} lcaset;
vector<int> ans;
int n, m, x, y, u, v, X[2000010], Y[2000010], lca[2000010], vis[2000010];
vector<int> G[2000010];
vector<pair<int, int> > queries[2000010];
void tarjan(int u) {
    vis[u]++;
    for (int i = 0; i < G[u].size(); i++) {
        if (!vis[G[u][i]]) {
            tarjan(G[u][i]);
            lcaset.fa[G[u][i]] = u;
        }
    }
    for (int i = 0; i < queries[u].size(); i++) {
        int v = queries[u][i].first, id = queries[u][i].second;
        if (vis[v] == 2 && !lca[id]) {
            lca[id] = lcaset.find(v);
        }
    }
    vis[u]++;
}
int d[2000010], dfn[2000010], dfe[2000010], times;
void dfs(int u, int f = 0) {
    dfn[u] = ++times;
    for (int v : G[u]) {
        if (v == f) continue;
        dfs(v, u);
    }
    dfe[u] = times;
}
void dfsxy(int u, int f = 0) {
    for (int v : G[u]) {
        if (v == f) continue;
        dfsxy(v, u);
    }
    for (int i = 0; i < queries[u].size(); i++) {
        int now = bt.query(dfn[queries[u][i].first]) + bt.query(dfn[queries[u][i].second]);
        if (now == 0) {
            ans.push_back(u);
            bt.modify(dfn[u], 1);
            bt.modify(dfe[u] + 1, -1);
            break;
        }
    }
}
int main() {
    scanf("%d", &n);
    lcaset.n = n;
    bt.n = n;
    for (int i = 1; i < n; i++) {
        scanf("%d%d", &x, &y);
        G[x].push_back(y);
        G[y].push_back(x);
    }
    dfs(1);
    lcaset.init();
    scanf("%d", &m);
    for (int i = 1; i <= m; i++) {
        scanf("%d%d", &X[i], &Y[i]);
        if (X[i] == Y[i]) lca[i] = X[i];
        else {
            queries[X[i]].push_back({Y[i], i});
            queries[Y[i]].push_back({X[i], i});
        }
    }
    tarjan(1);
    for (int i = 1; i <= n; i++) {
        queries[i].clear();
    }
    for (int i = 1; i <= m; i++) {
        // printf("lca of %d and %d is %d\n", X[i], Y[i], lca[i]);
        queries[lca[i]].push_back({X[i], Y[i]});
    }
    dfsxy(1);
    printf("%d\n", ans.size());
    for (int i = 0; i < ans.size(); i++) {
        printf("%d ", ans[i]);
    }
    return 0;
}