#include<bits/stdc++.h>
using namespace std;
struct Node{
	int l,r;
	bool bj;
}a[int(1e6+1)];
long long ans=0;
void dfs(int i,long long js)
{
	a[i].bj=1;
	if(a[i].l!=0)
	{
		dfs(a[i].l,js+1);
	}
	else
	{
		ans=max(js,ans);
		return;
	}
	if(a[i].r!=0)
	{
		dfs(a[i].r,js+1);
	}
	else
	{
		ans=max(js,ans);
		return;
	}
	return;
}
void read(int &x)
{
	x=0;
	int f=1;
	char ch=getchar();
	while
	((ch<'0'||ch>'9')&&ch!='-')
		ch=getchar();
	if(ch=='-')
		f=-1;
	while(ch>='0'&&ch<='9')
	{
		x*=10;
		x+=ch-'0';
		ch=getchar();
	}
	x*=f;
}
int main()
{
	int n,f=1;
	read(n);
	for(int i=1;i<=n;i++)
	{
		int x1,x2;
		read(x1);
		read(x2);
		if((x1==f)||(x2==f))
		{
			f=i;
		}
		a[i].l=x1;
		a[i].r=x2;
	}
	dfs(f,1);
	cout<<ans;
	return 0;
}