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

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

    def calc(free_group,o_group):
        res = bit[o_group]
        tmp = free_group
        while tmp:
            res += bit[tmp+o_group]
            tmp = (tmp-1)&free_group
        return res

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

    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))