#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
inline void smin(T &a, const U &b) {
  if (a > b) a = b;
}
template <typename T, typename U>
inline void smax(T &a, const U &b) {
  if (a < b) a = b;
}
template <class T>
inline void gn(T &first) {
  char c, sg = 0;
  while (c = getchar(), (c > '9' || c < '0') && c != '-')
    ;
  for ((c == '-' ? sg = 1, c = getchar() : 0), first = 0; c >= '0' && c <= '9';
       c = getchar())
    first = (first << 1) + (first << 3) + c - '0';
  if (sg) first = -first;
}
template <class T, class T1>
inline void gn(T &first, T1 &second) {
  gn(first);
  gn(second);
}
template <class T, class T1, class T2>
inline void gn(T &first, T1 &second, T2 &z) {
  gn(first);
  gn(second);
  gn(z);
}
template <class T>
inline void print(T first) {
  if (first < 0) {
    putchar('-');
    return print(-first);
  }
  if (first < 10) {
    putchar('0' + first);
    return;
  }
  print(first / 10);
  putchar(first % 10 + '0');
}
template <class T>
inline void printsp(T first) {
  print(first);
  putchar(' ');
}
template <class T>
inline void println(T first) {
  print(first);
  putchar('\n');
}
template <class T, class U>
inline void print(T first, U second) {
  printsp(first);
  println(second);
}
template <class T, class U, class V>
inline void print(T first, U second, V z) {
  printsp(first);
  printsp(second);
  println(z);
}
int power(int a, int b, int m, int ans = 1) {
  for (; b; b >>= 1, a = 1LL * a * a % m)
    if (b & 1) ans = 1LL * ans * a % m;
  return ans;
}
int main() {
  int n, m;
  const int NN = 1 << 20;
  static int dp[NN], a[20][20];
  static char s[20][22];
  gn(n, m);
  for (int i = 0; i < n; i++) cin >> s[i];
  for (int i = 0; i < n; i++)
    for (int j = 0; j < m; j++) gn(a[i][j]);
  memset(dp, 0x3f, sizeof dp);
  dp[0] = 0;
  for (int i = 0; i < (1 << n) - 1; i++) {
    if (dp[i] == 0x3f3f3f3f) continue;
    int u = (__builtin_ctz(~i)), v = 1 << u;
    for (int j = 0; j < m; j++) {
      smin(dp[i ^ v], dp[i] + a[u][j]);
      int st = i, sum = 0, mx = 0;
      for (int k = 0; k < n; k++)
        if (s[u][j] == s[k][j]) {
          st |= 1 << k;
          sum += a[k][j];
          smax(mx, a[k][j]);
        }
      smin(dp[st], dp[i] + sum - mx);
    }
  }
  println(dp[(1 << n) - 1]);
  return 0;
}
