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

for i in range(N):
    s=S[i]
    ind2=0
    c=0
    for ind in range(M):
        if s[ind]==T1[ind2]:
            ind2+=1
        else:
            c+=1
            if s[ind]==T1[ind2+1]:
                ind2+=2
            else:
                c=100
                break
    if c>=2:
        break
    
else:
    ANS+=1

    
for i in range(N):
    s=S[i]
    ind2=0
    c=0
    for ind in range(M):
        if s[ind]==T2[ind2]:
            ind2+=1
        else:
            c+=1
            if s[ind]==T2[ind2+1]:
                ind2+=2
            else:
                c=100
                break
    if c>=2:
        break
    
else:
    ANS+=1

print(ANS)