class UnionFindVerSize():
    def __init__(self, N):
        self._parent = [n for n in range(0, N)]
        self._size = [1] * N
        self.group = N

    def find_root(self, x):
        if self._parent[x] == x: return x
        self._parent[x] = self.find_root(self._parent[x])
        stack = [x]
        while self._parent[stack[-1]]!=stack[-1]:
            stack.append(self._parent[stack[-1]])
        for v in stack:
            self._parent[v] = stack[-1]
        return self._parent[x]

    def unite(self, x, y):
        gx = self.find_root(x)
        gy = self.find_root(y)
        if gx == gy: return

        self.group -= 1

        if self._size[gx] < self._size[gy]:
            self._parent[gx] = gy
            self._size[gy] += self._size[gx]
        else:
            self._parent[gy] = gx
            self._size[gx] += self._size[gy]

    def get_size(self, x):
        return self._size[self.find_root(x)]

    def is_same_group(self, x, y):
        return self.find_root(x) == self.find_root(y)

import sys,random
from collections import deque

def solve(N,M,_E):
    E = [(u-1,v-1) for u,v in _E]
    uf = UnionFindVerSize(N)
    D = [0] * N
    for u,v in E[::-1]:
        pu,pv = uf.find_root(u),uf.find_root(v)
        if pu!=pv:
            uf.unite(pu,pv)
            D[uf.find_root(pu)] = max(D[pu],D[pv]) + 1
        else:
            D[pu] += 1
    
    return max(D)

N,M = map(int,input().split())
E = [tuple(map(int,input().split())) for _ in range(M)]

print(solve(N,M,E))