import sys

# sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
# md = 998244353

def zeta(aa):
    n = len(aa).bit_length()-1
    res = aa[:]
    for i in range(n):
        for s in range(1 << n):
            if s >> i & 1: res[s] += res[s ^ 1 << i]
    return res

n,m=LI()
vv=LI()

aa=[0]*(1<<m)
for v in vv:
    s=0
    for i,c in enumerate(SI()):
        if c=="o":s|=1<<i
    aa[s]+=v

def chmax(i,val):
    if val>dp[i]:dp[i]=val

aa=zeta(aa)
dp=[0]*(1<<m)
mask=(1<<m)-1
for s in range(1<<m):
    for i in range(m):
        if s>>i&1:continue
        chmax(s|1<<i,dp[s]+(aa[mask^s]-aa[mask^s^1<<i])**2)

print(dp[-1])