#include<bits/stdc++.h>
using namespace std;
struct tree{
	int left,right;
}T[1000100];
int ans=1;
void dfs(int k,int deep)
{
	if(k==0)return;
	ans=max(ans,deep);
	dfs(T[k].left,deep+1);
	dfs(T[k].left,deep+1);
}
int main()
{
	int n;
	scanf("%d",&n);
	for(int i=1;i<=n;i++)scanf("%d%d",&T[i].left,&T[i].right);
	dfs(1,1);
	printf("%d",ans);
	return 0;
}