#include <bits/stdc++.h>
using namespace std;
int main(){
  int N, M;
  cin >> N >> M;
  vector<int> V(N);
  for (int i = 0; i < N; i++){
    cin >> V[i];
  }
  vector<string> S(N);
  for (int i = 0; i < N; i++){
    cin >> S[i];
  }
  vector<int> A(N, 0);
  for (int i = 0; i < N; i++){
    for (int j = 0; j < M; j++){
      if (S[i][j] == 'o'){
        A[i] |= 1 << j;
      }
    }
  }
  vector<long long> zeta(1 << M, 0);
  for (int i = 0; i < N; i++){
    zeta[A[i]] += V[i];
  }
  for (int i = 0; i < M; i++){
    for (int j = 0; j < (1 << M); j++){
      if ((j >> i & 1) == 1){
        zeta[j] += zeta[j - (1 << i)];
      }
    }
  }
  vector<long long> dp(1 << M, 0);
  for (int i = 0; i < (1 << M); i++){
    for (int j = 0; j < M; j++){
      if ((i >> j & 1) == 0){
        int i2 = i | (1 << j);
        int S = zeta[(1 << M) - 1 - i] - zeta[(1 << M) - 1 - i2];
        dp[i2] = max(dp[i2], dp[i] + (long long) S * S);
      }
    }
  }
  cout << dp[(1 << M) - 1] << endl;
}