#include <bits/stdc++.h>
#define ll long long
using namespace std;

vector<int> edges[100010];
bool visited[100010];
int ans = INT_MIN, maxim_1, maxim_2;
bool maxim_1_found = false;

ifstream fin("darb.in");
ofstream fout("darb.out");

void dfs(int x, int distanta) {
    if (visited[x] == false) {
        visited[x] = true;
        if (distanta > ans) {
            ans = distanta;
        }
        for (int i = 0; i < edges[x].size(); ++i) {
            dfs(edges[x][i], distanta + 1);
            if (ans > maxim_1 && x == 9) {
                maxim_2 = maxim_1;
                maxim_1 = ans;
                ans = 0;
            }
            else if(ans > maxim_2 && ans < maxim_1) {
                maxim_2 = ans;
                ans = 0;
            }
        }
    }
}

int main() {
    fin.tie(0);
    ios::sync_with_stdio(0);
    int n;
    fin >> n;
    for (int i = 1; i <= n - 1; ++i) {
        int x, y;
        fin >> x >> y;
        edges[x].push_back(y);
        edges[y].push_back(x);
    }
    dfs(9, 0);
    fout << maxim_1 + maxim_2 + 1;
    return 0;
}