#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define ll long long
ll mod=1000000007;
int inf=1000000007;
ll infl=1000000000000000007;
vector<int>G[1007];
int d[1007];
vector<int>res;
bool ok;
void dfs(int v,int o)
{
bool was=0;
d[v]=1;
for(auto u:G[v])
{
if(u==o) continue;
dfs(u,v);
d[v]=max(d[v],d[u]+1);
if(d[u]>2)
{
if(was) ok=0;
was=1;
}
}
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n,m,a,b;
cin>>n>>m;
if(m!=n-1)
{
cout<<"NO"<<endl;
return 0;
}
for(int i=0;i<n-1;i++)
{
cin>>a>>b;
G[a].pb(b);
G[b].pb(a);
}
vector<int>ans;
bool is=0;
for(int i=1;i<=n;i++)
{
ok=1;
res.clear();
dfs(i,0);
if(ok)
{
is=1;
}
}
if(!is) cout<<"NO"<<endl;
else
{
cout<<"YES"<<endl;
cout<<1<<endl<<1<<endl;
//for(auto x:ans) cout<<1<<" ";
}
return 0;
}
