#include <iostream>
#include <string>
using namespace std;
struct node{
	int left,right,depth;
};
struct node tree[10000000];
int main(){
	int n,ans=1;
	cin>>n;
	tree[1].depth=1;
	for(int i=1;i<=n;++i){
		int a,b;
		cin>>a>>b;
		tree[i].left=a;
		tree[i].right=b;
		tree[tree[i].left].depth=tree[i].depth+1;
		tree[tree[i].right].depth=tree[i].depth+1;
		if(tree[tree[i].left].depth>ans&&a!=0) ans=tree[tree[i].left].depth;
		if(tree[tree[i].right].depth>ans&&b!=0) ans=tree[tree[i].right].depth;
	}
	cout<<ans;
	return 0;
}