/**
* author: BERNARD B.01
**/
#include <bits/stdc++.h>
using namespace std;
#ifdef B01
#include "deb.h"
#else
#define deb(...)
#endif
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
if (m <= 2) {
cout << "YES" << '\n';
if (m == 0) {
cout << 1 << '\n';
cout << 1 << '\n';
} else if (m == 1) {
cout << 2 << '\n';
cout << 1 << '\n';
} else {
cout << 2 << '\n';
vector<int> deg(n);
int u, v;
cin >> u >> v;
--u; --v;
deg[u]++;
deg[v]++;
int uu, vv;
cin >> uu >> vv;
deg[uu]++;
deg[vv]++;
--uu; --vv;
cout << (deg[0] == 2 ? 1 : (deg[1] == 2 ? 2 : 3)) << '\n';
}
} else {
cout << "NO" << '\n';
}
return 0;
}
