import java.util.ArrayList;
import java.util.Scanner;

public class Main {
    static ArrayList<Integer>[] graph;
    static int[] d;
    static boolean[] visited;
    static int ans = 0;

    static void dfs(int v) {
        visited[v] = true;
        int max1 = -1;
        int max2 = -1;
        for (int i = 0; i < graph[v].size(); i++) {
            int to = graph[v].get(i);
            if (!visited[to]) {
                dfs(to);
                if (d[to] >= max1) {
                    int t = max1;
                    max1 = d[to];
                    max2 = t;
                } else if (d[to] > max2) {
                    max2 = d[to];
                }
            }
        }
        ans = Math.max(ans, (max1 + max2 + 2));
        d[v] = max1 + 1;
    }

    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        int n = s.nextInt();
        graph = new ArrayList[n];
        for (int i = 0; i < n; i++) {
            graph[i] = new ArrayList<Integer>();
        }
        d = new int[n];
        visited = new boolean[n];
        for (int i = 0; i < n - 1; i++) {
            int x = s.nextInt() - 1;
            int y = s.nextInt() - 1;
            graph[x].add(y);
            graph[y].add(x);
        }
        dfs(0);
        System.out.println(ans);
    }
}