// Shaazzz
#include<bits/stdc++.h>
using namespace std;
const int N = 1e6 + 10;
int n, k, H[N];
vector < int > Adj[N];
void DFS(int v, int p)
{
    for (int &u : Adj[v])
        if (u != p)
            H[u] = H[v] + 1,
            DFS(u, v);
}
int main()
{
    scanf("%d%d", &n, &k);
    for (int i = 1; i < n; i++)
    {
        int v, u;
        scanf("%d%d", &v, &u);
        Adj[v].push_back(u);
        Adj[u].push_back(v);
    }
    DFS(1, 0);
    int v = 0, d = 0;
    for (int i = 1; i <= n; i++)
        if (H[i] >= H[v])
            v = i;
    H[v] = 0; DFS(v, 0);
    for (int i = 1; i <= n; i++)
        d = max(d, H[i]);
    if (k <= d) return !printf("%d", k + 1);
    return !printf("%d", min((k + d + 2) / 2, n));
}

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