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):
        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 = 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):
        return self.find(x) == self.find(y)

    def get_size(self, x):
        x = self.find(x)
        return self.size[x]
    

N, M = map(int, input().split())
A, B = [0] * M, [0] * M
for i in range(M):
    A[i], B[i] = map(int, input().split())
A.reverse()
B.reverse()

U = UnionFind(N)
dp = [0] * N
for i in range(M):
    a, b = A[i], B[i]
    a, b = a - 1, b - 1
    if U.is_same(a, b):
        dp[U.find(a)] += 1
        continue
    v = max(dp[U.find(a)], dp[U.find(b)])
    U.union(a, b)
    dp[U.find(a)] = max(dp[U.find(a)], v + 1)
print(max(dp))