#include <bits/stdc++.h>
using namespace std;

const int N = 2e5 + 10;

int n, m;
vector<int> g[N], q[N];

int dep[N], fa[N][20], sz[N], dfn[N], dcnt;

void dfs(int u, int f) {
    dep[u] = dep[f] + 1;
    fa[u][0] = f;
    for(int i = 0; fa[u][i]; i ++)
        fa[u][i + 1] = fa[fa[u][i]][i];

    dfn[u] = ++dcnt;
    sz[u] = 1;
    for(int v : g[u])
        if(v != f) {
            dfs(v, u);
            sz[u] += sz[v];
        }
}

int lca(int u, int v) {
    if(dep[u] < dep[v]) swap(u, v);
    for(int j = 19; j >= 0; j --)
        if((dep[u] - dep[v]) >> j)
            u = fa[u][j];

    if(u == v) return u;
    for(int j = 19; j >= 0; j --) {
        if(fa[u][j] != fa[v][j]) {
            u = fa[u][j];
            v = fa[v][j];
        }
    }
    return fa[u][0];
}

int a[N], b[N];

vector<int> ans;

int tr[N];

void add(int p, int x) {
    while(p <= n) {
        tr[p] += x;
        p += p & -p;
    }
}

int query(int p) {
    int ret = 0;
    while(p > 0) {
        ret += tr[p];
        p -= p & -p;
    }
    return ret;
}


void solve(int u) {
    for(int v : g[u]) {
        if(v != fa[u][0])
            solve(v);
    }

    for(auto i : q[u]) {
        if(query(dfn[a[i]]) || query(dfn[b[i]])) continue;
        ans.push_back(u);
        add(dfn[u], 1);
        add(dfn[u] + sz[u], -1);
        break;
    }

}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    cin >> n >> m;
    for(int i = 1, u, v; i < n; i ++) {
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }

    dfs(1, 0);

    for(int i = 1; i <= m; i ++) {
        cin >> a[i] >> b[i];
        q[lca(a[i], b[i])].push_back(i);
    }

    solve(1);

    cout << ans.size() << "\n";
    for(int x : ans)
        cout << x << " ";
}