#include<bits/stdc++.h>

using namespace std;
const int N = 10e6+5;
typedef struct node
{
    int lchild;
    int rchild;
}treelist;

int d,d1=1,d2=1;
treelist tree[N];

void dfs(int i)
{

    if(tree[i].lchild != 0)
        dfs(tree[i].lchild),d1++;
    if(tree[i].rchild != 0)
        dfs(tree[i].rchild),d2++;
    d = max(d1,d2);
}
int main()
{
    int n,i;
    cin>>n;
    for(i = 1;i <= n; i++)
    {
        cin>>tree[i].lchild>>tree[i].rchild;
    }
    dfs(1);
    cout<<d;
    return 0;
}