#include <bits/stdc++.h>
using namespace std;
struct node {
  int point, w;
} p[30][30];
int n, m;
int s[30][30], w[30][30], Min[30], f[3000000];
int Get() {
  char c = getchar();
  while (!isalpha(c)) c = getchar();
  return c;
}
void init(int x, int y) {
  int t1 = 0, t2 = 0, mx = 0;
  for (int i = 1; i <= n; i++)
    if (s[i][y] == s[x][y]) {
      t1 |= 1 << (i - 1);
      t2 += w[i][y];
      mx = max(mx, w[i][y]);
    }
  p[x][y] = (node){t1, t2 - mx};
}
int Getlow(int x) {
  int ss[200];
  int num = 0;
  if (x == 0) return 1;
  while (x) {
    ss[++num] = x % 2;
    x /= 2;
  }
  ss[++num] = 0;
  for (int i = 1; i <= num; i++)
    if (ss[i] == 0) return i;
}
int main() {
  for (int i = 1; i <= 29; i++) Min[i] = 19240012;
  for (int i = 1; i <= 3000000 - 1; i++) f[i] = 30000000;
  cin >> n >> m;
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) s[i][j] = Get();
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) {
      cin >> w[i][j];
      Min[i] = min(Min[i], w[i][j]);
    }
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) init(i, j);
  f[0] = 0;
  for (int i = 0; i < (1 << n); i++) {
    int p_ = Getlow(i);
    f[i | (1 << (p_ - 1))] = min(f[i | (1 << (p_ - 1))], f[i] + Min[p_]);
    for (int j = 1; j <= m; j++)
      f[i | p[p_][j].point] = min(f[i | p[p_][j].point], f[i] + p[p_][j].w);
  }
  cout << f[(1 << n) - 1] << endl;
  return 0;
}
