I,R=input,range
M,N=map(int,I().split())
n=[[1]*N for i in R(N)]
for j in R(M):
	s=I();one=[];zero=[]
	for i in R(N):
		if s[i]>'0':one+=[i]
		else:zero+=[i]
	for i in one:
		for k in zero:n[i][k]=0
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]:
			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)