#include<iostream>
#include<algorithm>
#include<cstring>

using namespace std;

const int N=1e6+10;

struct node
{
	int fa,ch[2],deep;
};

int n,res;
node tree[N];

void get(int u,int dep)
{
	if(u==0)
		return;
	tree[u].deep=dep;
	res=max(res,dep);
	get(tree[u].ch[0],dep+1);
	get(tree[u].ch[1],dep+1);
	return;
}

int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		int a,b;
		cin>>a>>b;
		tree[i].ch[0]=a;
		tree[i].ch[1]=b;
		if(a)
			tree[a].fa=i;
		if(b)
			tree[b].fa=i;
	}
	get(1,1);
	cout<<res<<endl;
	return 0;
}