import java.io.*;
import java.util.*;
import java.util.stream.*;

public class Main {
    static int n;
    static int m;
    static int[] values;
    static int[] masks;
    static long[] dp;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        n = sc.nextInt();
        m = sc.nextInt();
        values = new int[n];
        for (int i = 0; i < n; i++) {
            values[i] = sc.nextInt();
        }
        masks = new int[n];
        for (int i = 0; i < n; i++) {
            char[] inputs = sc.next().toCharArray();
            for (int j = 0; j < m; j++) {
                if (inputs[j] == 'o') {
                    masks[i] += (1 << j);
                }
            }
        }
        dp = new long[1 << m];
        Arrays.fill(dp, -1);
        System.out.println(dfw(m, 0));
    }
    
    static long dfw(int idx, int v) {
        if (idx == 0) {
            return 0;
        }
        if (dp[v] < 0) {
            for (int i = 0; i < m; i++) {
                long sum = 0;
                for (int j = 0; j < n; j++) {
                    if ((masks[j] & (1 << i)) > 0 && (masks[j] & v) == 0) {
                        sum += values[j];
                    }
                }
                dp[v] = Math.max(dp[v], sum * sum + dfw(idx - 1, v | (1 << i)));
            }
        }
        return dp[v];
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}