import os,sys,random,threading
#sys.exit() 退出程序
#sys.setrecursionlimit(10**6) #调整栈空间
from random import randint,choice,shuffle
#randint(a,b)从[a,b]范围随机选择一个数
#choice(seq)seq可以是一个列表,元组或字符串,从seq中随机选取一个元素
#shuffle(x)将一个可变的序列x中的元素打乱
from copy import deepcopy
from io import BytesIO,IOBase
from types import GeneratorType
from functools import lru_cache,reduce
#reduce(op,迭代对象)
from bisect import bisect_left,bisect_right
#bisect_left(x) 大于等于x的第一个下标
#bisect_right(x) 大于x的第一个下标
from collections import Counter,defaultdict,deque
from itertools import accumulate,combinations,permutations
#accumulate(a)用a序列生成一个累积迭代器，一般list化前面放个[0]做前缀和用
#combinations(a,k)a序列选k个 组合迭代器
#permutations(a,k)a序列选k个 排列迭代器
from heapq import  heapify,heappop,heappush
#heapify将列表转为堆
from typing import Generic,Iterable,Iterator,TypeVar,Union,List
from string import ascii_lowercase,ascii_uppercase,digits
#小写字母，大写字母，十进制数字
from math import ceil,floor,sqrt,pi,factorial,gcd,log,log10,log2,inf
#ceil向上取整，floor向下取整 ，sqrt开方 ，factorial阶乘
from decimal import Decimal,getcontext
#Decimal(s) 实例化Decimal对象,一般使用字符串
#getcontext().prec=100 修改精度
from sys import stdin, stdout, setrecursionlimit
input = lambda: sys.stdin.readline().rstrip("\r\n")
MI = lambda :map(int,input().split())
li = lambda :list(MI())
ii = lambda :int(input())
mod = int(1e9 + 7) #998244353
inf = 1<<60
py = lambda :print("YES")
pn = lambda :print("NO")
DIRS = [(0, 1), (1, 0), (0, -1), (-1, 0)]  # 右下左上
DIRS8 = [(0, 1), (1, 1), (1, 0), (1, -1), (0, -1), (-1, -1), (-1, 0),(-1, 1)]  # →↘↓↙←↖↑↗



def bootstrap(f, stack=[]):   #yield
    def wrappedfunc(*args, **kwargs):
        if stack:
            return f(*args, **kwargs)
        else:
            to = f(*args, **kwargs)
            while True:
                if type(to) is GeneratorType:
                    stack.append(to)
                    to = next(to)
                else:
                    stack.pop()
                    if not stack:
                        break
                    to = stack[-1].send(to)
            return to
    return wrappedfunc


n=ii()

g=[[] for _ in range(n)]

for _ in range(n-1):
    u,v=li()
    u-=1
    v-=1
    g[u]+=[v]
    g[v]+=[u]

global res
res=inf

h=[0]*n


@bootstrap
def dfs(u,f):
    for v in g[u]:
        if v!=f:
            yield dfs(v,u)
            h[u]=max(h[u],h[v]+1)
    yield None
dfs(0,-1)

@bootstrap
def dfs2(u,f):
    global res
    fi=se=-1
    for v in g[u]:    #这个时候u是根，所以不需要管f，f也作为u的子节点的
        if h[v]>fi:
            se,fi=fi,h[v]
        elif h[v]>se:
            se=h[v]
    for v in g[u]:
        if v!=f:
            if h[v]==fi:
                d1=fi
                d2=se+1
                h[u]=se+1 #递归前换根，把h[u]换做是v为根时的情况
            else:
                d1=fi+1
                d2=h[v]
                h[u]=fi+1
            newd=max((d1+1)//2+(d2+1)//2+1,d1,d2)
            res=min(res,newd)
            yield dfs2(v,u)
    yield None
dfs2(0,-1)

print(res)