#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,ans;
struct tree{
int l,r;
}a[1005];
void dfs(int u,int deep)
{
if(u==0) return;
ans=max(ans,deep);
dfs(a[u].l,deep+1);
dfs(a[u].r,deep+1);
}
signed main()
{
cin>>n;
for(int i=1;i<=n;i++)
cin>>a[i].l>>a[i].r;
dfs(1,1);
cout<<ans;
return 0;
}