import sys
input=lambda:sys.stdin.readline().rstrip()
class unionFind:
    def __init__(self,N):
        self.N=N
        self.parent=[-1 for i in range(N)]
        self.size=[1 for i in range(N)]
    def find(self,x):
        path=[x]
        while self.parent[path[-1]]!=-1:
            path.append(self.parent[path[-1]])
        for i in path[:-1]:
            self.parent[i]=path[-1]
        return path[-1]
    def unite(self,x,y):
        roots=sorted([self.find(x),self.find(y)],key=lambda _:self.parent[_])
        if roots[0]!=roots[1]:
            self.parent[roots[0]]=roots[1]
            self.size[roots[1]]+=self.size[roots[0]]

N,M=map(int,input().split())
A=[list(map(lambda x:int(x)-1,input().split())) for i in range(M)][::-1]
U=unionFind(N)
mem={}
for i in range(N):
	mem[U.find(i)]=0
for i in A:
	temp=max(mem[U.find(i[0])],mem[U.find(i[1])])+1
	U.unite(i[0],i[1])
	mem[U.find(i[0])]=temp
print(max(mem.values()))