#include <bits/stdc++.h>
using namespace std;
#define int long long
#define inf 0x3F3F3F3F3F3F3F3F
const int MXN = 1e6 + 5;
const int LOG = 20;
int n;
int d[MXN], par[MXN], in[MXN];
vector<int> adj[MXN];
int bfs(int s)
{
fill(d + 1, d + n + 1, inf);
fill(par + 1, par + n + 1, 0);
fill(in + 1, in + n + 1, 0);
queue<int> q;
q.push(s);
d[s] = 0;
while (!q.empty())
{
int a = q.front();
q.pop();
for (int &v : adj[a])
{
if (d[v] > d[a] + 1)
{
d[v] = d[a] + 1;
par[v] = a;
q.push(v);
}
}
}
int x = max_element(d + 1, d + n + 1) - d;
while (x)
{
in[x] = 1;
x = par[x];
}
return x;
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
int m;
cin >> n >> m;
if (n == 1)
{
cout << "YES\n1\n1\n";
return 0;
}
if (n == 2)
{
cout << "YES\n2\n1 1\n";
return 0;
}
if (m > n - 1)
{
cout << "NO\n";
return 0;
}
for (int i = 1; i <= m; i++)
{
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
int d1, d2;
d2 = bfs(d1 = bfs(1));
for (int i = 1; i <= n; i++)
{
if (!in[i] && adj[i].size() > 1)
{
cout << "NO\n";
return 0;
}
}
cout << "YES\n1\n1\n";
}
