#include <iostream>
#include <algorithm>
#include <vector>
#include <stdlib.h>

using namespace std;
using ll = long long;
using ull = unsigned long long;
int maxi_depth = 0;
int saved = -1;

int dfs(vector<vector<int>> &graph, vector<int> &visited, vector<int> &dfs_answer, int v, int depth = 0) {
    depth++;
    if (depth > maxi_depth) {
        maxi_depth = depth;
        saved = v;
    }
    if (dfs_answer[v] != 0) return dfs_answer[v];
    visited[v] = true;
    int count = 0;
    int result = 0;
    for (int i = 0; i < graph[v].size(); i++) {
        if (!visited[graph[v][i]]) {
            count++;
            result = max(result, dfs(graph, visited, dfs_answer, graph[v][i], depth));
        }
    }
    if (count == 0) { //значит это лист
        dfs_answer[v] = 1;
        return 1;
    }
    else {
        return result + 1;
        dfs_answer[v] = result + 1;
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, M;
    cin >> N >> M; //N вершин и M километров

    vector<vector<int>> graph(N);
    vector<int> visited(N, 0);
    vector<int> dfs_answer(N, 0);

    for (int i = 0; i < N - 1; i++) {
        int beg, end;
        cin >> beg >> end;
        graph[beg - 1].push_back(end - 1);
        graph[end - 1].push_back(beg - 1);
    }

    int result = dfs(graph, visited, dfs_answer, graph[0][0]) + 1;
    visited.clear();
    dfs_answer.clear();

    vector<int> visited2(N, 0);
    vector<int> dfs_answer2(N, 0);

    result = dfs(graph, visited2, dfs_answer2, saved - 1) + 1;

    if (M < result) cout << M + 1;
    else {
        M = M - result;
        result += M / 2;
        cout << result;
    }

    return 0;
}