#include<vector>
#include<set>
#include<map>
#include<queue>
#include<string>
#include<algorithm>
#include<iostream>
#include<bitset>
#include<functional>
#include<chrono>
#include<numeric>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cassert>
#include<cmath>
#include<iomanip>
#include<random>
#include<ctime>
#include<complex>
#include<type_traits>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
typedef long long LL;
typedef double D;
#define all(v) (v).begin(), (v).end()
mt19937 gene(chrono::system_clock::now().time_since_epoch().count());
typedef complex<double> Complex;
#define fi first
#define se second
#define ins insert
#define pb push_back
inline char GET_CHAR(){
    const int maxn = 131072;
    static char buf[maxn],*p1=buf,*p2=buf;
    return p1==p2&&(p2=(p1=buf)+fread(buf,1,maxn,stdin),p1==p2)?EOF:*p1++;
}
inline int getInt() {
    int res(0);
    char c = getchar();
    while(c < '0') c = getchar();
    while(c >= '0') {
        res = res * 10 + (c - '0');
        c = getchar();
    }
    return res;
}
inline LL fastpo(LL x, LL n, LL mod) {
    LL res(1);
    while(n) {
        if(n & 1) {
            res = res * (LL)x % mod;
        }
        x = x * (LL) x % mod;
        n /= 2;
    }
    return res;
}
template<LL mod> struct Num {
	LL a;
	Num operator + (const Num & b) { return Num{(a + b.a) % mod}; }
	Num operator - (const Num & b) { return Num{(a - b.a + mod) % mod}; }
	Num operator * (const Num & b) { return Num{a * b.a % mod}; }
	Num operator / (const Num & b) { return Num{a * fastpo(b.a, mod - 2, mod) % mod}; }
	void operator += (const Num & b) {if((a += b.a) >= mod) a -= mod;}
	void operator -= (const Num & b) {if((a -= b.a) < 0) a += mod;}
	void operator *= (const Num & b) { a = a * b.a % mod; }
	void operator /= (const Num & b) { a = a * fastpo(b.a, mod - 2, mod) % mod; }
	void operator = (const Num & b) { a = b.a; }
	void operator = (const LL & b) { a = b; }
};
template<LL mod> ostream & operator << (ostream & os, const Num<mod> & a) {
	os << a.a;
	return os;
}
LL gcd(LL a, LL b) { return b ? gcd(b, a % b) : a; }

inline string itoa(LL x, int width = 0) {
	string res;
	if(x == 0) res.push_back('0');
	while(x) {
		res.push_back('0' + x % 10);
		x /= 10;
	}
	while((int)res.size() < width) res.push_back('0');
	reverse(res.begin(), res.end());
	return res;
}
const int _B = 131072;
char buf[_B];
int _bl = 0;
inline void flush() {
	fwrite(buf, 1, _bl, stdout);
	_bl = 0;
}
__inline void _putchar(char c) {
	if(_bl == _B) flush();
	buf[_bl++] = c;
}
inline void print(LL x, char c) {
	static char tmp[20];
	int l = 0;
	if(!x) tmp[l++] = '0';
	else {
		while(x) {
			tmp[l++] = x % 10 + '0';
			x /= 10;
		}
	}
	for(int i = l - 1; i >= 0; i--) _putchar(tmp[i]);
	_putchar(c);
}
typedef double C;
struct P {
	C x, y;
	void scan() {
		double _x, _y;
		scanf("%lf%lf", &_x, &_y);
		x = _x; y = _y;
	}
	void print() {
		cout << '(' << x << ' ' << y << ')' << endl;
	}
	P operator + (const P & b) const { return P{x + b.x, y + b.y}; }
	P operator - (const P & b) const { return P{x - b.x, y - b.y}; }
	C operator * (const P & b) const { return x * b.y - y * b.x; }
	C operator % (const P & b) const { return x * b.x + y * b.y; }
};
P operator * (const C & x, const P & b) { return P{x * b.x, x * b.y}; }
const int N = 300033;
const int LOG = 20;
const int mod = 1e9 + 7;
const int inf = 1e9 + 7;
int n, m;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
int rela[N];
int getr(int x) {
    int p = x;
    while(rela[p] != p) p = rela[p];
    int p1 = p; p = x;
    while(rela[p] != p) {
        int p2 = rela[p];
        rela[p] = p1;
        p = p2;
    }
    return p1;
}
int ans = n - 1;
vector<int> e[N];
int len[N][2], u[N][2], d[N], up[N], fa[N];
void dfs(int v, int mx) {
	int maxk[2] = {0, 0}, uk[2] = {0, 0};
	for(int y : e[v]) {
		if(y == fa[v]) continue;
		int k = d[y];
		if(k > maxk[0]) {
			maxk[1] = maxk[0];
			uk[1] = uk[0];
			maxk[0] = k;
			uk[0] = y;
		}else if(k > maxk[1]) {
			maxk[1] = k;
			uk[1] = y;
		}
	}
	for(int y : e[v]) {
		if(y != fa[v]) {
			int tmp = up[v];
			if(y == u[v][0]) tmp += len[v][1]; else tmp += len[v][0];
			int nwmx = max(mx, tmp);
			nwmx = max(nwmx, y == uk[0] ? maxk[1] : maxk[0]);
			//cout << y << ' ' << nwmx << ' ' << d[y] << endl;
			ans = min(ans, max(nwmx, max(d[y], (nwmx + 1) / 2 + 1 + (d[y] + 1) / 2)));
			dfs(y, nwmx);
		}
	}
}
int main() {

	scanf("%d", &n);
	ans = n -1 ;
	for(int i = 1; i < n; i++) {
		int x, y;
		scanf("%d%d", &x, &y);
		e[x].pb(y);
		e[y].pb(x);

	}

	vector<int> q;
	q.pb(1);
	for(int op = 0; op < n; op++) {
		int v = q[op];
		for(int y : e[v]) {
			if(y != fa[v]) {
				fa[y] = v;
				q.pb(y);
			}
		}
	}
	for(int i = n - 1; i >= 0; i--) {
		int v = q[i];
		if(len[v][0] + 1 > len[fa[v]][0]) {
			len[fa[v]][1] = len[fa[v]][0];
			u[fa[v]][1] = u[fa[v]][0];
			len[fa[v]][0] = len[v][0] + 1;
			u[fa[v]][0] = v;
		}else if(len[v][0] + 1 > len[fa[v]][1]) {
			len[fa[v]][1] = len[v][0] + 1;
			u[fa[v]][1] = v;
		}
		d[v] = max(d[v], len[v][0] + len[v][1]);
		d[fa[v]] = max(d[fa[v]], d[v]);
	}
	for(int i = 0; i < n; i++) {
		int v = q[i];
		if(v == 1) {
			up[v] = 0;
			continue;
		}
		up[v] = up[fa[v]] + 1;
		if(u[fa[v]][0] == v) {
			up[v] = max(up[v], 1 + len[fa[v]][1]);
			
		}else up[v] = max(up[v], 1 + len[fa[v]][0]);
	}
	dfs(1, 0);
	cout << ans << endl;
}