бусинки

#include <iostream>
#include <string>
#include <sstream>
#include <cmath>
#include <algorithm>
#include <memory.h>
#include <stdio.h>
#include <vector>
#include <stack>
#include <deque>
#include <queue>
#include <vector>
#include <set>
#include <iterator>
#include <map>
#include <iomanip>
#define int long long
#define sp system("pause")
#define pb push_back
#define double long double
#define endl "\n"
#define un unsigned
#define INF 1000000009
#define pii pair<int, int>
#define all(v) v.begin(), v.end()
using namespace std;

int n1;

istream& operator >> (istream& in, vector<pii>& a)
{
    for (int i = 0; i < n1; i++)
    {
        in >> a[i].first;

        a[i].second = i + 1;
    }

    return in;
}

ostream& operator << (ostream& out, vector<char>& a)
{
    for (int i = n1 - 1; i > -1; i--)
    {
        out << a[i];
    }

    return out;
}

int mark[100000];

vector<set<int>> vc;

int ans = 0;

void DFS(int v)
{
    for (int i : vc[v])
    {
        if (mark[i] == -1)
        {
            mark[i] = mark[v] + 1;

            ans = max(ans, mark[i]);

            DFS(i);
        }
    }

    return;
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie();
    cout.tie();
    cout.precision(7);

    int n;
    cin >> n;

    vc.resize(n);

    for (int i = 0; i < n - 1; i++)
    {
        int a, b;
        cin >> a >> b;

        a--;
        b--;

        vc[a].insert(b);
        vc[b].insert(a);
    }

    for (int i = 0; i < n; i++)
    {
        fill(mark, mark + n, -1);

        mark[i] = 1;

        DFS(i);
    }

    cout << ans;

    return 0;
}