#include<bits/stdc++.h>
using namespace std;
int tree[1000100];
int n,maxx=INT_MIN;
int main(){
	cin>>n;
	tree[1]=1;
	for(int i=1;i<=n;i++){
		int l,r;
		cin>>l>>r;
		if(l) tree[l]=tree[i]+1;
		if(r) tree[r]=tree[i]+1;
		maxx=max(maxx,tree[l]);
		maxx=max(maxx,tree[r]);
	}
	cout<<maxx;
	return 0;
}