#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2")
#define int long long
#define pii pair<int,int>
#define vi vector<int>
#define ff first
#define ss second
#define sp << " " <<
#define all(x) x.begin(),x.end()
#define big(x) ((int)(x.size()))
using namespace std;
const int MOD = 1e9+7, LIM = 1e6+1, inf = 2e18;
const int N = 1e3+1;
vi edges[N],c(N,-1);
bool dfs(int node,int col) {
if (c[node] != -1) return true;
c[node] = col;
int fl = 1;
for (auto it : edges[node]) {
fl &= dfs(it,col^1);
if (c[it] == c[node]) {
return false;
}
}
return fl;
}
void solve() {
int n,m;
cin >> n >> m;
for (int i=1;i<=m;i++) {
int a,b;
cin >> a >> b;
edges[a].push_back(b);
edges[b].push_back(a);
}
cout << (dfs(1,1)?"YES\n":"NO\n");
cout << 0 << '\n';
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
