/**
* 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 != n - 1) {
cout << "NO" << '\n';
return 0;
}
vector<vector<int>> g(n);
for (int i = 0; i < m; i++) {
int u, v;
cin >> u >> v;
--u; --v;
g[u].push_back(v);
g[v].push_back(u);
}
int d = 0, to = 0;
function<void(int, int, int)> Dfs = [&](int v, int pr, int dph) {
if (dph >= d) {
d = dph;
to = v;
}
for (int u : g[v]) {
if (u == pr) {
continue;
}
Dfs(u, v, dph + 1);
}
};
Dfs(0, -1, 0);
int a = to;
Dfs(to, -1, 0);
int b = to;
vector<int> que;
vector<int> dist(n, -1);
function<bool(int, int, int)> Mark = [&](int v, int pr, int tar) {
if (v == tar) {
que.push_back(v);
dist[v] = 0;
return true;
}
for (int u : g[v]) {
if (u == pr) {
continue;
}
if (Mark(u, v, tar)) {
que.push_back(v);
dist[v] = 0;
return true;
}
}
return false;
};
Mark(a, -1, b);
for (int b = 0; b < (int) que.size(); b++) {
for (int u : g[que[b]]) {
if (dist[u] == -1) {
dist[u] = dist[que[b]] + 1;
que.push_back(u);
}
}
}
if (*max_element(dist.begin(), dist.end()) > 1) {
cout << "NO" << '\n';
return 0;
}
cout << "YES" << '\n';
cout << 1 << '\n';
cout << 1 << '\n';
return 0;
}
