import sys
#input = sys.stdin.readline
#input = sys.stdin.buffer.readline #文字列はダメ
#sys.setrecursionlimit(1000000)
import math
#import bisect
#import itertools
#import random
#from heapq import heapify, heappop, heappush
from collections import defaultdict 
from collections import deque
#import copy #DeepCopy: hoge = [_[:] for _ in hogehoge]
#from functools import lru_cache
#@lru_cache(maxsize=None)
#MOD = pow(10,9) + 7
#MOD = 998244353
#dx = [1,0,-1,0]
#dy = [0,1,0,-1]
#dx8 = [1,1,0,-1,-1,-1,0,1]
#dy8 = [0,1,1,1,0,-1,-1,-1]

def shift(x):
    return x//2 + pow(2,15) * (x%2)

class UnionFind(object):
    def __init__(self, n=1):
        self.par = [i for i in range(n)]
        self.rank = [0 for _ in range(n)]
        self.size = [1 for _ in range(n)]
    def find(self, x):
        """
        x が属するグループを探索して親を出す。
        """
        if self.par[x] == x:
            return x
        else:
            self.par[x] = self.find(self.par[x])
            return self.par[x]
    def union(self, x, y):
        """
        x と y のグループを結合
        """
        x = self.find(x)
        y = self.find(y)
        if x != y:
            if self.rank[x] < self.rank[y]:
                x, y = y, x
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1
            self.par[y] = x
            self.size[x] += self.size[y]
    def is_same(self, x, y):
        """
        x と y が同じグループか否か
        """
        return self.find(x) == self.find(y)
    def get_size(self, x):
        """
        x が属するグループの要素数
        """
        x = self.find(x)
        return self.size[x]


def main():
    N,M = map(int,input().split())
    G = [[] for _ in range(N)]
    edges = []
    for i in range(M):
        u,v = map(int,input().split())
        u -= 1; v -= 1
        edges.append((u,v))
    
    uf = UnionFind(N)

    dic = defaultdict(int)
    for i in reversed(range(M)):
        u,v = edges[i]
        paru = uf.find(u)
        parv = uf.find(v)
        uf.union(u,v)
        par = uf.find(u)
        dic[par] = max(dic[paru], dic[parv]) + 1
        # print("X",dic[par])


    ans = max(dic.values())
    print(ans)
    

if __name__ == '__main__':
    main()