#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>
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<vector<long long>> zeta(1 << M, vector<long long>(M, 0));

    for (int i = 0; i < N; i++) {
        int num = 0;
        for (int j = 0; j < M; j++) {
            if (S[i][j] == 'o') {
                num += (1 << j);
            }
        }
        for (int j = 0; j < M; j++) {
            if (S[i][j] == 'o') {
                zeta[num][j] += V[i];
            }
        }
    }

    for (int i = 0; i < M; i++) {
        for (int j = 0; j < (1 << M); j++) {
            if ((j & (1 << i)) == 0) {
                for (int k = 0; k < M; k++) {
                    zeta[j ^ (1 << i)][k] += zeta[j][k];
                }
            }
        }
    }

    vector<long long> dp(1 << M, -(1LL << 60));
    dp[0] = 0;

    for (int i = 0; i < (1 << M); i++) {
        int pos = ((1 << M) - 1) ^ i;
        for (int j = 0; j < M; j++) {
            if ((pos >> j) & 1) {
                dp[i | (1 << j)] = max(dp[i | (1 << j)], dp[i] + zeta[pos][j] * zeta[pos][j]);
            }
        }
    }

    cout << dp[(1 << M) - 1] << endl;

    return 0;
}