Diameter of a tree

//In the Name of Allah Most Gracious, Most Merciful//
/*If you want something you've never had, you have  to do something you never did.*/

#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;





#define pb push_back
#define ll long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define MaxN 201007
#define INF 1e9
#define INFL 1e18
#define PI acos(-1)
#define mp make_pair

typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>ordered_set;

//const int fx[]= {+1,-1,+0,+0};
//const int fy[]= {+0,+0,+1,-1};
//const int fx[]={+0,+0,+1,-1,-1,+1,-1,+1};   // Kings Move
//const int fy[]={-1,+1,+0,+0,+1,+1,-1,-1};  // Kings Move
//const int fx[]={-2, -2, -1, -1,  1,  1,  2,  2};  // Knights Move
//const int fy[]={-1,  1, -2,  2, -2,  2, -1,  1}; // Knights Move


int gcd(int a, int b)
{
 return b ? gcd(b, a%b) : a;
}

ll bigmod(ll b,ll p,ll m)
{
    ll res=1LL%m;
    ll x=b%m;
    while(p)
    {
        if( p & 1LL )res=(res*x) % m;
        x=(x*x)%m;
        p >>=1LL;
    }
    return res;
}

int n;
vector<int>adj[2*MaxN];
int d,node;
bool visited[2*MaxN];


void dfs(int x,int dis)
{
    visited[x]=true;
    if(dis>d)
    {
        d=dis;
        node=x;
    }
    for(int i=0;i<adj[x].size();i++)
    {
        int v=adj[x][i];

        if(visited[v]==false)
        {
            dfs(v,dis+1);
        }
    }
}


int main()
{

   //  #ifndef ONLINE_JUDGE
   //    freopen("input.txt","r",stdin);
   //    freopen("output.txt","w",stdout);
  //   #endif
 	ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin>>n;
    for(int i=1;i<n;i++)
    {
        int x,y;
        cin>>x>>y;
        adj[x].pb(y);
        adj[y].pb(x);
    }
    d=0;
    node=0;
    dfs(1,0);
    memset(visited,false,sizeof visited);
    dfs(node,0);
    cout<<d<<endl;


//#ifdef LOCAL_DEFINE
  //  cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
// #endif
///Before submit=>
///    *check for integer overflow,array bounds
///    *check for n=1
}