#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, m; cin >> n >> m;
	vector<long long>a(n);
	rep(i, n)cin >> a[i];
	vector<string>s(n);
	vector<int>ok(n, 0);
	rep(i, n) {
		cin >> s[i];
		rep(j, m) {
			if ('o' == s[i][j])ok[i] |= 1 << j;
		}
	}
	vector<long long>zeta(1 << m);
	rep(i, n)zeta[ok[i]] += a[i];
	rep(j, m) {
		rep(i, 1 << m) {
			if (1 & (i >> j)) {
				zeta[i] += zeta[i & ~(1 << j)];
				//zeta[i] += zeta[i ^ (1 << j)];
			}
		}
	}
	vector<long long>dp(1 << m, -LINF);
	dp[0] = 0;
	int bit = (1 << m) - 1;
	rep(i, 1 << m) {
		rep(j, m) {
			if (1 & (i >> j))continue;
			int ni = i + (1 << j);
			long long val = zeta[bit ^i] - zeta[bit - ni];
			chmax(dp[i ^ (1 << j)], dp[i] + val * val);
		}
	}
	cout << dp[bit] << endl;
	return 0;
}