#include "bits/stdc++.h"
#define int long long
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
using namespace std;
const long long INF = 1ll << 60;
const int N = 1000 + 5;
int h[N], pr[N];
vector<int> adj[N], V[N], order;
bitset<N> leaf;
void dfs(int v, int p) {
for (auto u: adj[v]) if (u != p) {
h[u] = h[v] + 1;
pr[u] = v;
dfs(u, v);
}
}
signed main() {
ios::sync_with_stdio(0), cin.tie(0);
int n, m;
cin >> n >> m;
if (m >= n) {
cout << "NO\n";
return 0;
}
if (n <= 2) {
cout << "YES\n";
cout << n << '\n';
FOR(i, 0, n) cout << 1 << ' ';
return 0;
}
FOR(i, 1, n) {
int u, v; cin >> u >> v;
u--, v--;
adj[u].push_back(v);
adj[v].push_back(u);
}
FOR(i, 0, n) leaf[i] = adj[i].size() == 1;
FOR(i, 0, n) if (!leaf[i]) {
vector<int> t;
for (auto u: adj[i]) if (!leaf[u]) t.push_back(u);
adj[i] = t;
}
//is caterpillar?
FOR(i, 0, n) {
int ch = 0;
for (auto u: adj[i]) ch += adj[u].size() > 1;
if (ch >= 3) {
cout << "NO\n";
return 0;
}
}
int U, V;
FOR(i, 0, n) if (!leaf[i]) {
memset(h, -0x3f, sizeof h);
h[i] = 0;
dfs(i, i);
U = max_element(h, h + n) - h;
memset(h, -0x3f, sizeof h);
h[U] = 0;
dfs(U, U);
V = max_element(h, h + n) - h;
break;
}
//U, V is diam.
for (int t = V; t != U; t = pr[t]) {
order.push_back(t);
for (auto u: adj[t]) if (!leaf[u] && adj[u].size() == 1 && u != V && u != U)
order.push_back(u), order.push_back(t);
}
order.push_back(U);
cout << "YES\n";
cout << order.size() * 2 << '\n';
for (auto u: order) cout << u + 1 << ' ';
reverse(order.begin(), order.end());
for (auto u: order) cout << u + 1 << ' ';
cout << '\n';
return 0;
}
// this fills you with ....
