mod = 998244353


def main():
    import sys
    input = sys.stdin.readline

    def subst(A, B):
        j = 0
        res = 1
        for i, b in enumerate(B):
            if b != A[j]:
                if i == j:
                    j += 1
                    if b != A[j]:
                        res = 0
                        break
                else:
                    res = 0
                    break
            j += 1
        return res

    N, M = map(int, input().split())
    S_list = []
    for _ in range(N):
        S_list.append(input().rstrip('\n'))

    A, B = S_list[0], S_list[1]
    diff_idx_list = []
    for i in range(M):
        if A[i] != B[i]:
            diff_idx_list.append(i)
    i = diff_idx_list[0]
    j = diff_idx_list[-1]
    T_list = []
    if i == j:
        T_list.append("".join([A[:i], A[i], B[i], A[i+1:]]))
        T_list.append("".join([A[:i], B[i], A[i], A[i + 1:]]))
    else:
        T_list.append("".join([A[:i], B[i], A[i:j+1], A[j + 1:]]))
        T_list.append("".join([A[:i], A[i:j + 1], B[j], A[j + 1:]]))
        T_list.append("".join([A[:i], A[i], B[i:j + 1], A[j + 1:]]))
        T_list.append("".join([A[:i], B[i:j + 1], A[j], A[j + 1:]]))

    T_list = list(set(T_list))
    ans = 0
    for T in T_list:
        ok = 1
        for S in S_list:
            if not subst(T, S):
                ok = 0
                break
        ans += ok
    print(ans)


if __name__ == '__main__':
    main()