#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1);
int ans, pos[120000], fa[21][120000], tim, dep[120000], K, n, x, y;
vector<int> E[120000];
struct wph {
  bool operator()(const int x, const int y) { return pos[x] < pos[y]; }
};
set<int, wph> S;
void prep(int x, int ff) {
  fa[0][x] = ff;
  for (int i = 1; i <= 20; ++i) fa[i][x] = fa[i - 1][fa[i - 1][x]];
}
void dfs(int x, int ff) {
  pos[x] = ++tim;
  prep(x, ff);
  for (int i = 0; i < E[x].size(); ++i)
    if (E[x][i] != ff) {
      dep[E[x][i]] = dep[x] + 1;
      dfs(E[x][i], x);
    }
}
int pathlen(int x, int y) {
  int ans = dep[x] + dep[y];
  if (dep[x] < dep[y]) swap(x, y);
  for (int i = 20; i >= 0; --i)
    if ((dep[x] - dep[y]) >= 1 << i) x = fa[i][x];
  if (x == y) return ans - 2 * dep[x];
  for (int i = 20; i >= 0; --i)
    if (fa[i][x] != fa[i][y]) x = fa[i][x], y = fa[i][y];
  return ans - 2 * dep[fa[0][x]];
}
int calc(set<int>::iterator it) {
  int len = 0;
  auto p1 = it, p2 = it;
  if (p1 == S.begin()) p1 = S.end();
  p1--;
  len += pathlen(*p1, *it);
  p2++;
  if (p2 == S.end()) p2 = S.begin();
  len += pathlen(*p2, *it);
  len -= pathlen(*p2, *p1);
  return len;
}
int main() {
  scanf("%d%d", &n, &K);
  for (int i = 1; i <= n - 1; ++i) {
    scanf("%d%d", &x, &y);
    E[x].push_back(y);
    E[y].push_back(x);
  }
  dfs(1, 0);
  ans = 1;
  S.insert(1);
  int j = 1, size = 0;
  for (int i = 2; i <= n; ++i) {
    auto p = S.insert(i).first;
    size += calc(p);
    while (size / 2 + 1 > K) {
      p = S.find(j);
      size -= calc(p);
      S.erase(p);
      j++;
    }
    ans = max(ans, i - j + 1);
  }
  printf("%d\n", ans);
}
