#include<bits/stdc++.h>
using namespace std;
int n,ans;
struct node{
	int l,r,depth;
} a[100009];
int main(){
	scanf("%d", &n);
	a[1].depth = 1;
	for(int i = 1;i <= n;i++){
		scanf("%d%d", &a[i].l, &a[i].r);
		bool is_leaf = true;
		if(a[i].l != 0){
			a[a[i].l].depth = a[i].depth + 1;
			is_leaf = false;
		}
		if(a[i].r != 0){
			a[a[i].r].depth = a[i].depth + 1;
			is_leaf = false;
		}
		if(is_leaf){
			ans = max(ans,a[i].depth);
		}
	}
	printf("%d",ans);
	return 0;
}