#include <iostream>
#include <string>

using namespace std;
typedef long long ll;
ll dp[1<<20],fz[1<<20],val[200010],inf = 1000000000000000000;
int main(){
    int i,j,k,n,m; cin >> n >> m;
    for(i=0;i<n;i++) cin >> val[i];
    for(i=0;i<n;i++){
        string s; cin >> s;
        int x = 0;
        for(j=0;j<m;j++){
            if(s[j]=='o') x += 1<<j;
        }
        fz[x] += val[i];
    }
    for(j=0;j<m;j++){
        for(i=0;i<(1<<m);i++){
            if(i>>j&1) fz[i] += fz[i^(1<<j)];
        }
    }
    for(i=0;i<(1<<m);i++) dp[i] = -inf;
    dp[0] = 0;
    for(i=1;i<(1<<m);i++){
        for(j=0;j<m;j++){
            if(i>>j&1){
                ll num = fz[i] - fz[i^(1<<j)];
                dp[i] = max(dp[i],dp[i^(1<<j)] + num*num);
            }
        }
    }
    cout << dp[(1<<m) - 1] << "\n";
}