import sys
input = sys.stdin.readline

N,K=map(int,input().split())
S=[list(map(int,list(input().strip()))) for i in range(N)]

X=[]

for s in S:
    a=0
    for i in range(len(s)):
        a+=(5**i)*s[i]
    X.append(a)


USED=[0]*(5**8+1)

SET=set(X)

ANS=0

for i in range(5**8,-1,-1):
    if i in SET:
        if USED[i]==1:
            ANS+=1
        USED[i]=1
    if USED[i]==1:
        for j in range(8):
            if (i%(5**(j+1)))//(5**j)!=0:
                USED[i-(5**j)]=1

print(ANS)