class UnionFindWithDp:
	def __init__(self, n):
		self.n = n
		self.dp = [0] * 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:
			self.dp[x] += 1
			return
		if self.parents[x] > self.parents[y]:
			x, y = y, x
		self.parents[x] += self.parents[y]
		self.dp[x] = max(self.dp[x], self.dp[y]) + 1
		self.parents[y] = x

n, m = map(int,input().split())
edges = []
for i in range(m):
	u, v = map(int,input().split())
	u -= 1
	v -= 1
	edges.append((u, v))

uf = UnionFindWithDp(n)
for i in range(m-1,-1,-1):
	u, v = edges[i]
	uf.union(u, v)

ans = 0
for i in range(n):
	ans = max(ans, uf.dp[i])
print(ans)