from collections import defaultdict

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):#self.parentsに要素数を記録しているのでほぼO(1)でできる
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):#o(N)かかって非常に遅いです
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        group_members = defaultdict(list)
        for member in range(self.n):
            group_members[self.find(member)].append(member)
        return group_members

    def __str__(self):
        return '\n'.join(f'{r}: {m}' for r, m in self.all_group_members().items())
from collections import deque
N,M = map(int,input().split())
nxedge =[[] for _ in range(M)]
uf = UnionFind(N)
board = []
memo = [-1] * N
for _ in range(M):
    u,v = map(int,input().split())
    board.append((u-1,v-1))
for i in reversed(range(M)):
    u,v = board[i]
    if uf.same(u,v):
        nxedge[i].append(memo[uf.find(u)])
        memo[uf.find(u)] = i
    else:
        if memo[uf.find(u)] != -1:
            nxedge[i].append(memo[uf.find(u)])
        if memo[uf.find(v)] != -1:
            nxedge[i].append(memo[uf.find(v)])
        uf.union(u,v)
        memo[uf.find(u)] = i
dp = [1] * M
q = deque()
q.append(0)
while q:
    now = q.popleft()
    for nx in nxedge[now]:
        dp[nx] = dp[now] + 1
        q.append(nx)
print(max(dp))