import sys
input = sys.stdin.readline


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

# UnionFind

Group = [i for i in range(N+1)] # グループ分け
Nodes = [1]*(N+1) # 各グループのノードの数

def find(x):
    while Group[x] != x:
        x=Group[x]
    return x

def Union(x,y):
    if find(x) != find(y):
        if Nodes[find(x)] < Nodes[find(y)]:
            
            Nodes[find(y)] += Nodes[find(x)]
            Nodes[find(x)] = 0
            Group[find(x)] = find(y)
            
        else:
            Nodes[find(x)] += Nodes[find(y)]
            Nodes[find(y)] = 0
            Group[find(y)] = find(x)

ANS=[0]*(N+1)

for a,b in E[::-1]:
    x=find(a)
    y=find(b)

    Union(a,b)

    ANS[find(a)]=max(ANS[x],ANS[y])+1

print(max(ANS))