#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;
vector<int> adj[N], V[N];
void dfs(int v, int p) {
V[v] = {0};
for (auto u: adj[v]) if (u != p) {
dfs(u, v);
V[v].push_back(V[u][0] + 1);
}
sort(V[v].rbegin(), V[v].rend());
}
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) {
FOR(j, 0, n) V[j].clear();
dfs(i, i);
if (V[i].size() >= 3 && V[i][2] >= 2) {
assert(0);
cout << "NO\n";
return 0;
}
}
cout << "YES\n";
cout << 2 * n - 4 << '\n';
FOR(i, 1, n - 1) cout << i + 1 << ' ';
FOR(i, 1, n - 1) cout << n - i << ' ';
cout << '\n';
return 0;
}
//Reading this fills you with DETERMINATION
//20:06:46
