using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[] NMi => ReadLine().Split().Select(c => int.Parse(c) - 1).ToArray();
    static int[][] NMap(int n) => Enumerable.Repeat(0, n).Select(_ => NMi).ToArray();
    static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m) = (c[0], c[1]);
        var map = NMap(m);

        var tree = new List<int>[m];
        for (var i = 0; i < tree.Length; ++i) tree[i] = new List<int>();

        var uf = new UnionFindTree(n);
        var isBridge = new bool[m];
        for (var i = m - 1; i >= 0; --i)
        {
            var pa = uf.info[uf.GetRoot(map[i][0])];
            var pb = uf.info[uf.GetRoot(map[i][1])];
            if (pa != int.MaxValue) tree[i].Add(pa);
            if (pb != int.MaxValue && pb != pa) tree[i].Add(pb);
            uf.Unite(map[i][0], map[i][1], i);
        }
        var dep = new int[m];
        DFS(0, tree, dep);
        WriteLine(dep.Max() + 1);
    }
    static void DFS(int cur, List<int>[] tree, int[] dep)
    {
        foreach (var next in tree[cur])
        {
            dep[next] = dep[cur] + 1;
            DFS(next, tree, dep);
        }
    }
    class UnionFindTree
    {
        int[] roots;
        public int[] info;
        public UnionFindTree(int size)
        {
            roots = new int[size];
            info = Enumerable.Repeat(int.MaxValue, size).ToArray();
            for (var i = 0; i < size; ++i) roots[i] = -1;
        }
        public int GetRoot(int a)
        {
            if (roots[a] < 0) return a;
            roots[a] = GetRoot(roots[a]);
            info[roots[a]] = Math.Min(info[roots[a]], info[a]);
            return roots[a];
        }
        public bool IsSameTree(int a, int b)
        {
            return GetRoot(a) == GetRoot(b);
        }
        public bool Unite(int a, int b, int info)
        {
            var x = GetRoot(a);
            var y = GetRoot(b);
            this.info[x] = Math.Min(this.info[x], info);
            this.info[y] = Math.Min(this.info[y], info);
            if (x == y) return false;
            if (-roots[x] < -roots[y]) { var tmp = x; x = y; y = tmp; }
            roots[x] += roots[y];
            roots[y] = x;
            return true;
        }
        public int GetSize(int a)
        {
            return -roots[GetRoot(a)];
        }
    }
}