#include <cstdio>
#include <cstring>
int max;//最终的结果
struct node{
    int left, right;
}Node[1000010];
void dfs(int a, int cen){
    if(!a)  return;
    ++cen, max = max > cen ? max : cen; //统计信息
    if(Node[a].left)    dfs(Node[a].left,cen);
    if(Node[a].right)  dfs(Node[a].right,cen);
}
int main(){
    int n;
    scanf("%d", &n);
    char hash[n + 1];
    memset(hash, 0, sizeof(hash));
    for(int i = 1;i <= n; ++i){
        scanf("%d %d",&Node[i].left, &Node[i].right);
        hash[Node[i].left] = 1, hash[Node[i].right] = 1;
    }
    int root;
    for(int i = 1;i <= n; ++i)  //找根节点
        if(hash[i] == 0){root = i;break;}
    max = 0;
    dfs(root, 0);
    printf("%d\n",max);
    return 0;
}