#include<iostream>
#include<cstring>
using namespace std;
#define MAX 1000
int lt[MAX];
int rt[MAX];
void built(int i){
   cin>>lt[i];
   cin>>rt[i];
}
void dfs(int num,int &deepth,int &max){
    deepth++;
    if(lt[num]==0&&rt[num]==0){
        if(deepth>max){
            max=deepth;
        }
        deepth--;
        return ;
    }
    if(lt[num]!=0){
        dfs(lt[num],deepth,max);
    }
    
    if(rt[num]!=0){
        dfs(rt[num],deepth,max);
    }
    
    deepth--;
    return;
}
int main(){
    memset(lt,0,sizeof(lt));
    memset(rt,0,sizeof(rt));
    int n,i=1;
    cin>>n;
    int deepth=0;
    int max=0;
    while(n--){
        built(i);
        i++;
    }
    dfs(1,deepth,max);
    cout<<max;
    return 0;
}