#include <bits/stdc++.h>
using namespace std;
#define LCBorz ios_base::sync_with_stdio(false); cin.tie(0);
#define int long long
#define all(x) x.begin(), x.end()
#define endl '\n'
const int N=200005;
const int INF=1e18;
vector<int> adj[N],vis(N),a[N];
void dfs(int k,int pa,int deep){
vis[k]=1;
a[k].push_back(deep);
for(int j:adj[k]){
if(j==pa)continue;
dfs(j,k,deep+1);
a[k].push_back(a[j][0]);
}
sort(all(a[k]),greater<int>());
}
int32_t main() {
LCBorz;
int n,m;cin>>n>>m;
if(m>=n){
cout<<"NO"<<endl;
return 0;
}
if(n==1){
cout<<"YES\n1\n1\n";
return 0;
}
if(n==2){
cout<<"YES\n2\n1 1\n";
return 0;
}
for(int i=1;i<n;i++){
int a,b;cin>>a>>b;
adj[a].push_back(b);
adj[b].push_back(a);
}
for(int i=1;i<=n;i++){
for(int j=1;j<=n;j++){
a[j].clear();
}
dfs(i,i,0);
if(a[i].size()<3){
continue;
}
if(a[i][2]>=3){
cout<<"NO"<<endl;
return 0;
}
}
cout<<"YES\n1\n1";
return 0;
}
