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

ifstream fin("darb.in");
ofstream fout("darb.out");
vector <int> edgesList[100001];
int maxx;

void dfs(int current, int sum) {
    for (int i = 0; i < edgesList[current].size(); i++)
        dfs(edgesList[current][i], sum + 1);
    maxx = max(maxx, sum);
}

int main() {
    int numOfVertices, v, w;

    cin >> numOfVertices;
    for (int i = 1; i < numOfVertices; i++) {
        cin >> v >> w;
        edgesList[v].push_back(w);
    }

    int max1 = 0, max2 = 0;
    for (int i = 0; i < edgesList[1].size(); i++) {
        int current = 1;
        dfs(edgesList[1][i], current);

        if (maxx > max1)
            max2 = max1, max1 = maxx;
        else if (maxx > max2)
            max2 = maxx;
        maxx = 0;
    }

    cout << max1 + max2 + 1;

    return 0;
}