#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,b) for(int i=0;i<b;i++)
#define rrep(i,b) for(int i=b-1;i>=0;i--)
#define rep1(i,b) for(int i=1;i<b;i++)
#define repx(i,x,b) for(int i=x;i<b;i++)
#define fore(i,a) for(auto i:a)
#define fore1(i,a) for(auto &i:a)
#define rng(x) (x).begin(), (x).end()
#define rrng(x) (x).rbegin(), (x).rend()
#define sz(x) ((int)(x).size())
#define pb push_back
#define fi first
#define se second

using namespace std;
using namespace atcoder;

using ll = long long;
template<typename T> using mpq = priority_queue<T, vector<T>, greater<T>>;
template<typename T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<typename T> bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<typename T> ll sumv(const vector<T>&a){ll res(0);for(auto&&x:a)res+=x;return res;}
bool yn(bool a) { if(a) {cout << "Yes" << endl; return 1;} else {cout << "No" << endl; return 0;}}
#define dame { cout << "No" << endl; return 0;}
#define dame1 { cout << -1 << endl; return 0;}
#define test(x) cout << "test" << x << endl;
#define deb(x,y) cout << x << " " << y << endl;
#define deb3(x,y,z) cout << x << " " << y << " " << z << endl;
#define deb4(x,y,z,x2) cout << x << " " << y << " " << z << " " << x2 << endl;
#define out cout << ans << endl;
#define outv fore(yans , ans) cout << yans << "\n";
#define show(x) cerr<<#x<<" = "<<x<<endl;
#define showv(v) {fore(vy , v) {cout << vy << " ";} cout << endl;}
#define showv2(v) fore(vy , v) cout << vy << "\n";
using pll = pair<ll,ll>;
using pil = pair<int,ll>;
using pli = pair<ll,int>;
using pii = pair<int,int>;
using tp = tuple<int ,int ,int>;
using vi = vector<int>;
using vl = vector<ll>;
using vs = vector<string>;
using vb = vector<bool>;
using vpii = vector<pii>;
using vpli = vector<pli>;
using vpll = vector<pll>;
using vpil = vector<pil>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<ll>>;
using vvs = vector<vector<string>>;
using vvb = vector<vector<bool>>;
using vvpii = vector<vector<pii>>;
using vvpli = vector<vector<pli>>;
using vvpll = vector<vpll>;
using vvpil = vector<vpil>;
using mint = modint998244353;
using vm = vector<mint>;
using vvm = vector<vector<mint>>;
vector<int> dx={1,0,-1,0,1,1,-1,-1},dy={0,1,0,-1,1,-1,1,-1};
ll gcd(ll a, ll b) { return a?gcd(b%a,a):b;}
ll lcm(ll a, ll b) { return a/gcd(a,b)*b;}
const double eps = 1e-10;
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;

int main(){
    int n,m; cin>>n>>m;

    vl v(n);
    rep(i,n) cin>>v[i];

    int l = 1 << m;

    vvl sum(l , vl(m+1));

    rep(i,n){
        string s; cin>>s;

        ll tmp = 0;

        rep(j,m) if (s[j] == 'o') tmp += (1 << j);

        sum[tmp][0] += v[i]; 
    }

    rep1(i,m+1){
        rep(j,l){
            sum[j][i] += sum[j][i-1];
            if ((j >> (i-1) & 1) == 1){
                int nj = j - (1 << (i-1));
                sum[j][i] += sum[nj][i-1];
            }
        }
    }

    vvi st(m+1);

    rep(i,l){
        int cnt = 0;
        rep(j,m) if ((i >> j & 1) == 1) cnt++;
        st[cnt].pb(i);
    }

    int nj = l-1 - 0;

    vl dp(l);

    dp[0] = 0;

    rep1(i,m+1){
        fore(y , st[i]){
            int yj = l - 1 - y;
            ll sumy = sum[yj][m];

            rep(k , m){
                if ((y >> k & 1) == 1){
                    int ny = y - (1 << k);
                    int nyj = l - 1 - ny;
                    ll sumny = sum[nyj][m];

                    ll diff = sumny - sumy;
                    chmax(dp[y] , dp[ny] + diff * diff);
                }
            }
        }
    }

    cout << dp[l-1] << endl;


    return 0;
}