#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <assert.h>

#include <iostream>

using namespace std;

#pragma warning(disable:4996)

typedef struct NODE
{
	int le = 0,
		ri = 0;
}node;


node nodes[100000 + 1];//节点0当守卫节点

int stack(node nodes[],int n,int deep);
int max(int a, int b) { return a > b ? a : b; }

int main()
{
	int nodenum = 0;
	cin >> nodenum;
	for (int i = 1; i <= nodenum; i++)
	{
		cin >> nodes[i].le >> nodes[i].ri;
	}
	cout<<stack(nodes, 1, 0);
	return 0;
}

int stack(node nodes[], int n, int deep)
{
	if (nodes[n].le == 0 || nodes[n].ri == 0)
		return deep + 1;
	else
		return max(stack(nodes,nodes[n].le,deep+1),
					stack(nodes,nodes[n].ri,deep+1));
}