1 #include <bits/stdc++.h>
 2 
 3 using namespace std;
 4 
 5 const int N = 1e6 + 10;
 6 
 7 int ok = 0;
 8 
 9 int n;
10 struct node
11 {
12     int l, r;
13 } t[N];
14 
15 void dfs(int i, int s)
16 {
17     if(i == 0) return;
18     ok = max(ok, s);
19     dfs(t[i].l, s + 1);
20     dfs(t[i].r, s + 1);
21 }
22 signed main()
23 {
24     scanf("%d", &n);
25     for(int i = 1; i <= n; ++i) scanf("%d%d", &t[i].l, &t[i].r);
26     dfs(1, 1);
27 
28     printf("%d", ok);
29 
30     return 0;
31 }