//#include <iostream>
#include <fstream>
#include <queue>
#include <stack>
#include <tuple>
#include <algorithm>

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

int findDiameter(std::queue<size_t> tree[], size_t root, size_t n)
{
    std::stack< std::tuple< size_t, size_t, size_t > > st;
    int diameter = 0;

    st.push(std::make_tuple(root, 0U, 0U));
    while(!st.empty())
    {
        const auto nodeId = std::get<0>(st.top());
        if(!tree[nodeId].empty())
        {
            st.push(std::make_tuple(tree[nodeId].front(), 0, 0));
            tree[nodeId].pop();
        }
        else
        {
            diameter = std::get<1>(st.top()) + std::get<2>(st.top()) + 1;
            //std::cout<<std::get<1>(st.top()) << ' ' << std::get<2>(st.top()) << '\n';

            //std::cout<<diameter<<'\n';
            auto max = std::max(std::get<1>(st.top()), std::get<2>(st.top()));
            st.pop();

            if(!st.empty())
            {
                auto& value = std::get<1>(st.top()) < std::get<2>(st.top()) ?
                              std::get<1>(st.top()) : std::get<2>(st.top());

                value = value <= max ? max + 1 : value;
            }
        }
    }

    return diameter;
}

int main()
{
    auto n = 0U;
    auto x = 0U;
    auto y = 0U;
    fin>>n;

    std::queue<size_t> tree[n+1];

    while(true)
    {
        fin >> x;
        fin >> y;
        if( fin.eof() ) break;

        //std::cout<< "x: " << x << ' ' << "y: " << y << '\n';
        tree[x].push(y);
    }

    /*for(auto i = 1U; i <= n; ++i)
    {
        std::cout<<i <<": ";
        std::for_each(tree[i].begin(), tree[i].end(), [](auto j){
                      std::cout<< j <<' ';
        });

        std::cout<<'\n';
    }*/

    auto diameter = findDiameter(tree, 1, n);
    fout << diameter <<'\n';

    return 0;
}