#include <iostream>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <string>
#include <fstream>
using namespace std;
int map[3005][3005];
int END[3005],P;
int visit[3005],key,ans=0;
void dfs(int v,int step)
{
    if(END[v])
	{
		if(step>ans) ans=step;
		return ;
    }
    for(int i=1;i<=key;i++)
		if(!visit[i]&&map[v][i])
		{
			visit[i]=1;
			dfs(i,step+1);
			visit[i]=0;
        }
}
int main()
{
	ifstream fin("stroll.in");
	ofstream fout("stroll.out");
    memset(END,0,sizeof(END));
    memset(visit,0,sizeof(visit));
    memset(map,0,sizeof(map));
    fin>>P;
    key=P;
    for(int i=0;i<P-1;i++)
	{
		int a,b,c;
        fin>>a>>b>>c;
        if(b==0)
		{
			map[a][key]=1;
			END[key]=1;
			key++;
        }
        if(b!=0) map[a][b]=1;
        if(c==0)
	    { 
			map[a][key++]=1;
			END[key]=1;
			key++;
	    }
        if(c!=0) map[a][c]=1; 
    }
    visit[1]=1;
    dfs(1,0);
    fout<<ans<<endl;
    return 0;
}