#include <bits/stdc++.h>
using namespace std;
namespace io {
inline char nc() {
  static char buf[100000], *p1 = buf, *p2 = buf;
  return p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 100000, stdin), p1 == p2)
             ? EOF
             : *p1++;
}
template <class I>
inline void fr(I &num) {
  num = 0;
  register char c = nc();
  register int p = 1;
  while (c < '0' || c > '9') c == '-' ? p = -1, c = nc() : c = nc();
  while (c >= '0' && c <= '9') num = num * 10 + c - '0', c = nc();
  num *= p;
}
template <class I>
inline I Max(I p, I q) {
  return p > q ? p : q;
}
template <class I>
inline I Min(I p, I q) {
  return p < q ? p : q;
}
template <class I>
inline I A(I x) {
  return x < 0 ? -x : x;
}
template <class I>
inline void sp(I &p, I &q) {
  I x = p;
  p = q, q = x;
}
template <class I>
inline void ckMax(I &p, I q) {
  p = (p > q ? p : q);
}
template <class I>
inline void ckMin(I &p, I q) {
  p = (p < q ? p : q);
}
};  // namespace io
using io ::A;
using io ::ckMax;
using io ::ckMin;
using io ::fr;
using io ::Max;
using io ::Min;
using io ::nc;
using io ::sp;
const int N = 1 << 18 | 5, lim = 1 << 18;
int n, h[N], nxt[N], adj[N], rd[N], t, u, v, f[N][2], fa[N], ans;
inline void add() {
  nxt[++t] = h[u], h[u] = t, adj[t] = v, nxt[++t] = h[v], h[v] = t, adj[t] = u;
}
inline void dfs(const int x) {
  f[x][0] = 0, f[x][1] = 1;
  for (register int i = h[x], j; i; i = nxt[i])
    if ((j = adj[i]) ^ fa[x])
      fa[j] = x, dfs(j),
      ckMax(ans,
            Max(Max(f[x][0] + f[j][0], f[x][1] + f[j][0]), f[x][0] + f[j][1])),
      ckMax(f[x][0], Max(f[j][0], f[j][1]) + rd[x] - 2),
      ckMax(f[x][1], f[j][0] + 1);
  ckMax(ans, f[x][1]);
}
int main() {
  scanf("%d", &n);
  for (register int i = 1; i < n; ++i)
    scanf("%d%d", &u, &v), add(), ++rd[u], ++rd[v];
  dfs(1), printf("%d", ans);
  return 0;
}
