#include <bits/stdc++.h>
#define nmax 100007

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

int n, viz[nmax], d[nmax];
vector <int> L[nmax];
queue <int> q;

void Citire()
{
    int x, y;
    fin >> n;
    for (int i = 1; i <= n; i++)
    {
        fin >> x >> y;
        L[x].push_back(y);
        L[y].push_back(x);
    }
}

void BFS(int nod)
{
    int k;
    d[nod] = 1;
    viz[nod] = 1;
    q.push(nod);
    while (!q.empty())
    {
        k = q.front();
        q.pop();
        for (auto i : L[k])
            if (!viz[i])
            {
                q.push(i);
                viz[i] = 1;
                d[i] = d[k] + 1;
            }
    }
}

int main()
{
    int i, m1, m2;
    Citire();
    BFS(1);

    m1 = d[2];
    m2 = d[1];
    /// m1 > m2
    for (i = 3; i <= n; i++)
        if (d[i] > m1)
        {
            m2 = m1;
            m1 = d[i];
        }
        else if (d[i] > m2)
            m2 = d[i];

    fout << m1 + m2 - 1 << "\n";
    fin.close();
    fout.close();
    return 0;
}