#include <bits/stdc++.h>
using namespace std;
const int maxn = 25;
string str[maxn];
int a[maxn][maxn];
long long dp[1 << 20];
int mask[26], tot[26], big[26], cnt[26], candi[26];
int Min[maxn];
int main() {
  int n, m;
  cin >> n >> m;
  for (int i = 1; i <= n; i++) {
    cin >> str[i];
  }
  memset(Min, 0x3f, sizeof(Min));
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      cin >> a[i][j];
      Min[i] = min(Min[i], a[i][j]);
    }
  }
  for (int i = 0; i < (1 << n); i++) {
    int tmp = 0;
    for (int j = 0; j < n; j++) {
      if (i >> j & 1) tmp += Min[j + 1];
    }
    dp[i] = tmp;
  }
  for (int i = 1; i <= m; i++) {
    memset(mask, 0, sizeof(mask));
    memset(tot, 0, sizeof(tot));
    memset(big, 0, sizeof(big));
    memset(cnt, 0, sizeof(cnt));
    for (int j = 1; j <= n; j++) {
      int c = str[j][i - 1] - 'a';
      cnt[c]++;
      mask[c] |= (1 << (j - 1));
      tot[c] += a[j][i];
      big[c] = max(big[c], a[j][i]);
    }
    int idx = 0;
    for (int j = 0; j < 26; j++) {
      if (cnt[j]) candi[idx++] = j;
    }
    for (int j = 0; j < (1 << n); j++) {
      for (int k = 0; k < idx; k++) {
        int u = candi[k];
        dp[j | mask[u]] = min(dp[j | mask[u]], dp[j] + (tot[u] - big[u]));
      }
    }
  }
  cout << dp[(1 << n) - 1] << endl;
  return 0;
}
