#include <bits/stdc++.h>
using namespace std;
struct node {
	int id;
	int layer;
};
int n;
node s[100500];
int ans = 0;
int main() {
	cin >> n;
	int lchild, rchild;
	for (int i = 1; i <= n; ++i) {
		s[i].id = i;
		s[i].layer=1;
	}
	for (int i = 1; i <= n; ++i) {
		cin >> lchild >> rchild;
		if (lchild != 0) {
			s[lchild].layer = s[i].layer + 1;
		}
		if (rchild != 0) {
			s[rchild].layer = s[i].layer + 1;
		}
	}
	for (int i = 1; i <= n; ++i) {
		ans = max(ans, s[i].layer);
	}
	cout << ans;
	return 0;
}