import sys
input = sys.stdin.readline

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

for i in range(M):
    if S[0][i]!=S[1][i]:
        T1=S[0][:i]+S[1][i]+S[0][i:]
        T2=S[1][:i]+S[0][i]+S[1][i:]
        break

ANS=0
SET=set()

for i in range(M+1):
    SET.add(T1[:i]+T1[i+1:])



for i in range(N):
    if S[i] in SET:
        True
    else:
        break
else:
    ANS+=1

    
SET=set()

for i in range(M+1):
    SET.add(T2[:i]+T2[i+1:])



for i in range(N):
    if S[i] in SET:
        True
    else:
        break
else:
    ANS+=1

print(ANS)