def zeta_to_small(N,A):
    res = [a for a in A]
    for i in range(N):
        t = 2**i
        for j in range(1<<N):
            if j&t:
                res[j-t] += res[j]
    return res

def solve(N,M,V,S):
    box = [0 for i in range(1<<M)]

    for i in range(N):
        t = 0
        for j in range(M):
            if S[i][j]=="x":
                t += 1<<j
        box[t] += V[i]

    zeta_box = zeta_to_small(M,box)

    dp = [0 for S in range(2**M)]
    ALL = 2**M-1
    for S in range(1,2**M):
        done = ALL - S
        for j in range(M):
            if S>>j & 1:
                tmp = zeta_box[done] - zeta_box[done + 2**j]
                dp[S] = max(dp[S],dp[S-2**j]+tmp*tmp)

    return dp[-1]

import sys

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

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