/* -*- coding: utf-8 -*-
 *
 * 1752.cc:  No.1752 Up-Down Tree - yukicoder
 */

#include<cstdio>
#include<vector>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 100000;

/* typedef */

typedef vector<int> vi;

/* global variables */

vi nbrs[MAX_N];
int ps[MAX_N], cis[MAX_N], ss[MAX_N];
int x0[MAX_N], x1[MAX_N], xi0[MAX_N], xi1[MAX_N];
int y0[MAX_N], yi0[MAX_N], y1[MAX_N], yi1[MAX_N];
int dp[MAX_N];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);

  for (int i = 1; i < n; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    u--, v--;
    nbrs[u].push_back(v);
    nbrs[v].push_back(u);
  }

  ps[0] = -1;
  for (int u = 0; u >= 0;) {
    vi &nbru = nbrs[u];
    int up = ps[u];

    if (cis[u] < nbru.size()) {
      int v = nbru[cis[u]++];
      if (v != up) {
	ps[v] = u;
	u = v;
      }
    }
    else {
      ss[u]++;

      int ux = 1;
      if (x0[u] > 0) {
	ux = x0[u];
	if (x1[u] > 0) ux += x1[u] + 1;
	else if (ss[u] - x0[u] >= 2) ux += 2;
      }

      int uy = x0[u] + 1;
      if (y0[u] > 0) {
	int uy0 = y0[u];
	if (x0[u] > 0 && xi0[u] != yi0[u]) uy0 += x0[u] + 1;
	else if (x1[u] > 0 && xi1[u] != yi0[u]) uy0 += x1[u] + 1;
	uy = max(uy, uy0);

	if (y1[u] > 0) {
	  int uy1 = y1[u];
	  if (x0[u] > 0 && xi0[u] != yi1[u]) uy1 += x0[u] + 1;
	  else if (x1[u] > 0 && xi1[u] != yi1[u]) uy1 += x1[u] + 1;
	  uy = max(uy, uy1);
	}
      }
      dp[u] = uy;
      
      if (up >= 0) {
	ss[up] += ss[u];

	if (x0[up] < ux) {
	  x1[up] = x0[up], xi1[up] = xi0[up];
	  x0[up] = ux, xi0[up] = u;
	}
	else if (x1[up] < ux)
	  x1[up] = ux, xi1[up] = u;

	if (y0[up] < uy) {
	  y1[up] = y0[up], yi1[up] = yi0[up];
	  y0[up] = uy, yi0[up] = u;
	}
	else if (y1[up] < uy)
	  y1[up] = uy, yi1[up] = u;
      }

      u = up;
    }
  }

  printf("%d\n", dp[0]);
  //for (int u = 0; u < n; u++) printf("%d ", dp[u]); putchar('\n');
  return 0;
}