## https://yukicoder.me/problems/no/1912


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

    # 各Nについて使える箱をbitmask化する
    bit_sums = [0] * (2 ** M)
    for i in range(N):
        bit = 0
        s = S[i]
        for m in range(M):
            if s[m] == "o":
                bit |= (1 << m)
        bit_sums[bit] += V[i]

    # 高速ゼータ変換で任意の箱の集合Sの中に収まる範囲でしか入らないスライムVの総和を計算
    zz = [[0] * (2 ** M) for _ in range(M + 1)]
    for i in range(2 ** M):
        zz[0][i] = bit_sums[i]
    for j in range(M):
        for i in range(2 ** M):
            if i & (1 << j) > 0:
                zz[j + 1][i] = zz[j][i - (1 << j)] + zz[j][i]
            else:
                zz[j + 1][i] = zz[j][i]

    # dp[選ばれていない箱S]についてdpを解く
    dp = [0] * (2 ** M)
    for s in range(2 ** M):
        for i in range(M):
            if s & (1 << i) > 0:
                s_ = s - (1 << i)
                dp[s] = max(dp[s], dp[s_] + (zz[-1][s] - zz[-1][s_]) ** 2)
    print(dp[-1])



        














if __name__ == "__main__":
    main()