#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<queue>
#include<iomanip>
#include<map>
#define re register
#define ll long long
using namespace std;
struct po
{int nxt,to,dis;
};
map<pair<int,int>,int> m;
po edge[4000001];
int q[1000001],head[1000001],dis[300001],b[300001],temp[400001][3];
int n,s,t,r,st,to,ans,maxx,num;
inline int read()
{int x=0,c=1;char ch=' ';while((ch<'0'||ch>'9')&&ch!='-')ch=getchar();while(ch=='-')c*=-1,ch=getchar();while(ch>='0'&&ch<='9')x=x*10+ch-'0',ch=getchar();return x*c;
}
inline void add_edge(int from,int to,int dis)
{edge[++num].nxt=head[from];edge[num].to=to;edge[num].dis=dis;head[from]=num;
}
inline void finish(int id,int x,int y)
{int s=m[make_pair(x,y)];if(s){add_edge(s,id,1);add_edge(id,s,1);m.erase(m.find(make_pair(x,y)));}elsem[make_pair(x,y)]=id;
}
inline void spfa(int x)
{memset(dis,127,sizeof(dis));memset(b,0,sizeof(b));int front=0,tail=1;dis[x]=0;q[tail]=x;b[x]=1;while(front<tail){int now=q[++front];b[now]=0;for(re int i=head[now];i;i=edge[i].nxt){int u=edge[i].to;if(dis[u]>edge[i].dis+dis[now]){dis[u]=edge[i].dis+dis[now];if(!b[u]){b[u]=1;q[++tail]=u;}}}}
}
inline void bfs(int x)
{memset(b,0,sizeof(b));int front=0,tail=1;temp[tail][1]=x;temp[tail][2]=1;b[x]=1;while(front<tail){int now=temp[++front][1];int dep=temp[front][2];if(dep>maxx){st=now;maxx=dep;}for(re int i=head[now];i;i=edge[i].nxt){int u=edge[i].to;if(!b[u]){b[u]=1;temp[++tail][1]=u;temp[tail][2]=dep+1;}}}
}
int main()
{n=read();for(re int i=1;i<=n-2;i++){s=read();t=read();r=read();if(s>t)swap(s,t);if(s>r)swap(s,r);if(t>r)swap(t,r);finish(i,s,t);finish(i,s,r);finish(i,t,r);}bfs(1);maxx=0;bfs(st);cout<<maxx;
}