def check(N,M,S,T):
    for i in range(N):
        search = 0
        for j in range(M+1):
            if search==M:
                break
            if S[i][search]==T[j]:
                search += 1
        if search!=M:
            return 0
    return 1


def solve(N,M,S):
    for j in range(M):
        if S[0][j]!=S[1][j]:
            T0 = S[0][:j] + S[1][j] + S[0][j:]
            T1 = S[1][:j] + S[0][j] + S[1][j:]
            res = check(N,M,S,T0) + check(N,M,S,T1)
            return res

N,M = map(int,input().split())
S = [input() for _ in range(N)]
print(solve(N,M,S))