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

    def subseq(s, x):
        p = 0
        for c in s:
            if p < len(x) and x[p] == c:
                p += 1
        return p == len(x)

    def check(x):
        for s in S:
            if not subseq(x, s):
                return False
        return True

    for i in range(M):
        for j in range(N):
            if S[0][i] != S[j][i]:
                ans = 0
                ans += check(S[0][:i] + S[0][i] + S[j][i:])
                ans += check(S[j][:i] + S[j][i] + S[0][i:])
                print(ans)
                return


if __name__ == '__main__':
    main()