I,R=input,range
M,N=map(int,I().split())
n=[(1<<N)-1]*N
for j in R(M):
	b=int(I(),2)
	for i in R(N):
		if b>>i&1:n[i]&=b
c=N
P=list(R(N))
H=[0]*N
def r(i):
	m=P[i]
	while i!=m:P[i]=i=P[m];m=P[i]
	return i
for i in R(N):
	for j in R(N):
		if n[i]>>j&1:
			u,v=r(i),r(j)
			if H[v]<H[u]:u,v=v,u
			H[v]+=H[u]==H[v];P[u]=v;c-=u!=v
print(c)