N,M = map(int, input().split())
V = list(map(int, input().split()))
l = [0] * (1<<M)#現在使った箱の部分集合がiの時、使っているスライム
for i in range(N):
    S = list(input())
    tmp = 0
    for j in range(M):
        if S[j] == "o":
            tmp += (1<<j)
    l[tmp] += V[i]

for i in range(M):
    for j in range(1<<M):

        if j&(1<<i):
            l[j] += l[j^(1<<i)]
dp = [0] * (1<<M)#ここまでで使った箱
mask = (1<<M) -1 
for i in range(1<<M):
    for j in range(M):

        if (i>>j) & 1:
            continue

        dp[i|(1<<j)] = max(dp[i|(1<<j)],dp[i] + (l[mask^i]-l[mask^i^(1<<j)])**2)#mask^iでまだ使ってない箱+箱j、mask^i^(1<<j)で箱j抜き
print(dp[-1])