#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define fi first
#define si second
#define ar array
#define pb push_back
typedef pair<int,int> pi;
typedef tuple<int,int,int> ti;  
typedef vector<int> vi;
template<typename T> bool chmin(T &a, T b){return (b < a) ? a = b, 1 : 0;}
template<typename T> bool chmax(T &a, T b){return (b > a) ? a = b, 1 : 0;}
void debug_out() {cerr<<endl;}
template <typename Head, typename... Tail>
void debug_out(Head _H, Tail... _T) {cerr<<" "<<to_string(_H);debug_out(_T...);}
#define debug(...) cerr<<"["<<#__VA_ARGS__<<"]:",debug_out(__VA_ARGS__)
const int N = 200010, LOG = 18;
int n, m, ans;
vector<int> g[N], nodes;
vector<ar<int,3>> big;

int cnt = 1;
int pre[N], post[N], dep[N];
int up[N][LOG];
void dfs(int x, int p) {
    pre[x] = cnt++;
    up[x][0] = p;
    if (p != -1) dep[x] = dep[p] + 1;
    for (int i = 1; i < LOG; ++i) {
        if (up[x][i - 1] == -1) continue;
        up[x][i] = up[up[x][i - 1]][i - 1];
    }
    for (int i: g[x]) {
        if (i == p) continue;
        dfs(i, x);
    }
    post[x] = cnt - 1;
}

int jump(int x, int k) {
    for (int i = 0; i < LOG; ++i) {
        if (x == -1) return -1;
        if (k & (1 << i)) x = up[x][i];
    }
    return x;
}

int lca(int a, int b) {
    if (dep[a] < dep[b]) swap(a, b);
    a = jump(a, dep[a] - dep[b]); 
    if (a == b) return a;
    for (int i = LOG - 1; i >= 0; --i) {
        if (up[a][i] == -1 || up[b][i] == -1) continue;
        if (up[a][i] != up[b][i]) {
            a = up[a][i];
            b = up[b][i];
        }
    }
    return up[a][0];
}

int fw[N], fw2[N];
void update(int x, int y, int v) { 
    for (int tx=x; tx < N; tx += tx&(-tx)) fw[tx] += v, fw2[tx] -= v*(x-1);
    for (int ty=y+1; ty < N; ty += ty&(-ty)) fw[ty] -= v, fw2[ty] += v*y; 
}
int sum(int x) {
    int res = 0;
    for (int tx=x; tx; tx -= tx&(-tx)) res += fw[tx]*x + fw2[tx];
    return res;
}
int query(int x, int y) {
    return sum(y) - sum(x - 1);
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cin.exceptions(ios::badbit|ios::failbit);
    cin >> n >> m;
    for (int i = 0; i < n - 1; ++i) {
        int u, v; cin >> u >> v;
        g[u].pb(v);
        g[v].pb(u);
    }
    memset(up, -1, sizeof up);
    dfs(1, -1);
    for (int i = 0; i < m; ++i) {
        int u, v; cin >> u >> v;
        big.pb({lca(u, v), u, v});
    }
    sort(big.begin(), big.end(), [&](ar<int,3> x, ar<int,3> y) {
        return dep[x[0]] > dep[y[0]];
    });
    for (auto i: big) {
        int u = i[1], v = i[2];
        if (query(pre[u], pre[u]) || query(pre[v], pre[v])) continue;
        update(pre[i[0]], post[i[0]], 1);
        ++ans;
        nodes.pb(i[0]);
    }
    cout << ans << '\n';
    for (auto i: nodes) cout << i << ' ';
    return 0;
}