#include<bits/stdc++.h>
using namespace std;
const int N = 1.5e6 + 10, mod = 1e9+7;
int n, k;
vector<int> G[N];
bool mark[N];
bool Close;
void Dfs(int v, int p = -1, int d = 1)
{
if(Close || d > k) return;
if(d <= k && d != 1)
Close |= mark[v];
for(int u : G[v])
if(u != p)
Dfs(u, v, d + 1);
}
void dFs(int v, int p = -1, int d = 1)
{
if(Close || d > k) return;
if(d == k)
Close = true;
for(int u : G[v])
{
if(u == p) continue;
if(!mark[u])
dFs(u, v, d + 1);
}
}
bool check(int v)
{
bool seen[n + 1] = {};
memset(seen, false, sizeof(seen));
seen[v] = 1;
vector<int> level = {v};
int l = 1;
vector<int> vec;
Close = false;
while(level.size())
{
// cerr << l << endl;
if(l == 1)
for(int x : level)
vec.push_back(x);
vector<int> nl;
for(int x : level)
for(int u : G[x])
if(!seen[u])
seen[u] = 1, nl.push_back(u);
l = l % k + 1;
level = nl;
}
// cerr << "k = " << k << endl;
// cerr << "vec = ";
for(int u : vec)
{
// cerr << u << ' ';
mark[u] = true;
}
// cerr << endl;
for(int i = 1; i <= n; i ++)
if(mark[i])
Dfs(i);
else
dFs(i);
for(int v : vec)
mark[v] = false;
return !Close;
}
int main()
{
cin >> n >> k;
if(k == 2)
{
cout << "YES\n";
cout << 2 << endl;
return 0;
}
for(int i = 1; i < n; i ++)
{
int a, b;
cin >> a >> b;
G[a].push_back(b);
G[b].push_back(a);
}
int ans = 0;
for(int v = 1; v <= n; v++)
ans += check(v);
cout << (ans == 0 ? "NO" : "YES") << endl;
cout << ans << endl;
return 0;
}
