#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
typedef int BTDataType;
typedef struct BTNode
{
    BTDataType x;
    struct BTNode *left;
    struct BTNode *right;
} BTNode;
typedef BTNode *Tree;

// 建立二叉树结点
Tree CreatTree(BTDataType x);

int main()
{
    Tree T = CreatTree(1);
    Tree temp;
    Tree AT[1000000];
    AT[1] = T;
    int n, l, r, height;

    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
    {
        scanf("%d%d", &l, &r);
        if (l != 0)
        {
            temp = (Tree)malloc(sizeof(struct BTNode));
            temp->left = NULL;
            temp->right = NULL;
            temp->x = AT[i]->x + 1;
            AT[i]->left = temp;
            AT[l] = temp;
            if (temp->x > height)
                height = temp->x;
        }
        if (r != 0)
        {
            temp = (Tree)malloc(sizeof(struct BTNode));
            temp->left = NULL;
            temp->right = NULL;
            temp->x = AT[i]->x + 1;
            AT[i]->right = temp;
            AT[r] = temp;
            if (temp->x > height)
                height = temp->x;
        }
    }

    printf("%d", height);
    return 0;
}

BTNode *CreatTree(BTDataType x)
{
    BTNode *temp = (BTNode *)malloc(sizeof(BTNode));
    if (temp == NULL)
    {
        perror("CreatTree::malloc");
        exit(-1);
    }
    temp->x = x;
    temp->left = temp->right = NULL;
    return temp;
}