#include<bits/stdc++.h>
using namespace std;
using ll = long long;
vector <int> g[1005];
bool used[1005], ok = 1;
int ln[1005], mx = 0;
void dfs (int v, int pr = 0) {
used[v] = 1, ln[v] = ln[pr] + 1;
mx = max(mx, ln[v]);
for (auto it : g[v]) {
if (!used[it]) dfs(it, v);
}
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n, m; cin >> n >> m;
ln[0] = 0;
for (int i = 1; i <= m; i++) {
int u, v; cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
} if (m != n - 1) {
cout << "NO\n";
return 0;
} dfs(1);
if (mx >= 2 || n == 1) {
cout << "YES\n1\n1";
return 0;
} else cout << "NO\n";
return 0;
}
