N,M=map(int,input().split())
V=list(map(int,input().split()))
S=[input() for i in range(N)]
zeta=[[0]*M for i in range(1<<M)]
for s,v in zip(S,V):
    num=0
    for i in range(M):
        if s[i]=="o":
            num+=1<<i
    for i in range(M):
        if s[i]=="o":
            zeta[num][i]+=v
for i in range(M):
    for j in range(1<<M):
        if (j&(1<<i))==0:
            for k in range(M):
                zeta[j^(1<<i)][k]+=zeta[j][k]
dp=[-(1<<60)]*(1<<M)
dp[0]=0
for i in range(1<<M):
    pos=((1<<M)-1)^i
    for j in range(M):
        if (pos>>j)&1:
            dp[i|(1<<j)]=max(dp[i|(1<<j)],dp[i]+zeta[pos][j]*zeta[pos][j])
print(dp[-1])