n,m = map(int,input().split())
es = [list(map(int,input().split())) for i in range(m)]

p = [-1]*(n+1)
def find(x):
  if p[x] < 0:
    return x
  else:
    p[x] = find(p[x])
    return p[x]
def union(x,y):
  x = find(x)
  y = find(y)
  if x == y:
    return
  if p[x] > p[y]:
    x,y = y,x
  p[x] += p[y]
  p[y] = x

from collections import defaultdict
ps = defaultdict(int)
for i in range(m)[::-1]:
  u,v = es[i]
  uu,vv = find(u),find(v)
  mx = max(ps[uu],ps[vv])
  union(uu,vv)
  ps[find(uu)] = mx + 1

print(max(ps.values()))