#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll
using ii = pair<int, int>;
using iii = pair<ii, int>;
#pragma GCC optimize("O3")
constexpr int MAXN = 200'000 + 5;
constexpr int INF = 1e18 + 5;
constexpr int LOG = 20;
int cntr = -1;
vector<int> adjlist[MAXN];
int pa[LOG][MAXN];
int pre[MAXN];
int post[MAXN];
int depth[MAXN];
int fenwick[MAXN];
void upd(int x) {
int l = pre[x];
int r = post[x];
l += 1, r += 1;
auto point_update = [&](int p, int v) {
for (; p <= MAXN; p += (p & -p)) fenwick[p] += v;
};
point_update(l, 1);
point_update(r+1, -1);
}
bool rq(int x) {
x = pre[x];
x += 1;
int tot = 0;
for (; x > 0; x &= x-1) {
tot += fenwick[x];
}
return tot > 0;
}
void dfs(int x) {
pre[x] = ++cntr;
for (int ch : adjlist[x]) {
if (ch == pa[0][x]) continue;
pa[0][ch] = x;
depth[ch] = depth[x] + 1;
for (int i = 1; i < LOG; ++i) pa[i][ch] = pa[i-1][pa[i-1][ch]];
dfs(ch);
}
post[x] = cntr;
}
int lca(int a, int b) {
// WLOG depth[a] <= depth[b]
if (depth[a] > depth[b]) swap(a, b);
int diff = depth[b] - depth[a];
for (int i = LOG-1; i >= 0; --i) {
if ((diff >> i) & 1) b = pa[i][b];
}
if (a == b) return a;
for (int i = LOG-1; i >= 0; --i) {
if (pa[i][a] != pa[i][b]) {
a = pa[i][a], b = pa[i][b];
}
}
return pa[0][a];
}
signed main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
for (int i = 0; i < LOG; ++i) pa[i][1] = 1;
depth[1] = 0;
int N, M; cin >> N >> M;
for (int i = 0; i < N-1; ++i) {
int u, v; cin >> u >> v;
adjlist[u].emplace_back(v);
adjlist[v].emplace_back(u);
}
dfs(1);
vector<iii> paths(M);
for (int i = 0; i < M; ++i) {
int a, b; cin >> a >> b;
int l = lca(a, b);
paths[i] = iii{ii{a, b}, l};
}
sort(paths.begin(), paths.end(), [&](const iii &a, const iii &b) {
return depth[a.second] > depth[b.second];
});
vector<int> rem;
for (iii path : paths) {
auto [u, v] = path.first;
int l = path.second;
if (rq(u) || rq(v)) continue;
rem.emplace_back(l);
upd(l);
}
cout << rem.size() << '\n';
for (int i : rem) cout << i << ' ';
}
/*
9 4
1 2
2 3
2 6
3 4
4 5
4 7
6 9
7 8
6 2
5 3
4 8
5 9
*/
