#include <bits/stdc++.h>
#define vi vector<int>
// #define int long long
#define pb push_back
#define all(x) (x).begin(), (x).end()
using namespace std;
const int N = 1e3+5;
vi graf[N];
int njgl=0;
int naj=0;
int dfs(int u, int p=-1)
{
int mx = 0;
for (int v:graf[u])
if (v!=p)
mx=max(mx, dfs(v, u));
return mx+1;
}
signed main()
{
int n, m;
cin >> n >> m;
for (int i = 0; i < m; i++)
{
int u, v;
cin >> u >> v;
graf[u].pb(v);graf[v].pb(u);
}
for (int i = 1; i <= n; i++)
{
int cnt = 0;
for (auto v:graf[i])
{
if (dfs(v, i)>=2)
cnt++;
}
if (cnt>2)
{
cout << "NO\n";
return 0;
}
}
cout << "YES\n1\n1\n";
return 0;
}
