#include <bits/stdc++.h>
using namespace std;
struct fastIO {
  inline fastIO operator>>(int& num) {
    num = 0;
    char c = getchar();
    while (c != '-' && (c < '0' || c > '9')) c = getchar();
    bool foo = 0;
    if (c == '-') {
      foo = 1;
      c = getchar();
    }
    while (c >= '0' && c <= '9') {
      num = (num << 3) + (num << 1) + c - '0';
      c = getchar();
    }
    if (foo) num = -num;
    return *this;
  }
  inline fastIO operator>>(long long& num) {
    num = 0;
    char c = getchar();
    while (c != '-' && (c < '0' || c > '9')) c = getchar();
    bool foo = 0;
    if (c == '-') {
      foo = 1;
      c = getchar();
    }
    while (c >= '0' && c <= '9') {
      num = (num << 3) + (num << 1) + c - '0';
      c = getchar();
    }
    if (foo) num = -num;
    return *this;
  }
  inline fastIO operator>>(float& num) {
    scanf("%f", &num);
    return *this;
  }
  inline fastIO operator>>(double& num) {
    scanf("%lf", &num);
    return *this;
  }
  inline fastIO operator>>(long double& num) {
    scanf("%Lf", &num);
    return *this;
  }
  inline fastIO operator>>(char& num) {
    num = getchar();
    while (num == ' ' || num == '\n') num = getchar();
    return *this;
  }
  inline fastIO operator>>(char* num) {
    int cnt = 0;
    char c = getchar();
    while (c == ' ' || c == '\n') c = getchar();
    while (c != ' ' && c != '\n') {
      num[cnt++] = c;
      c = getchar();
    }
    num[cnt] = 0;
    return *this;
  }
  inline fastIO operator>>(string& num) {
    cin >> num;
    return *this;
  }
  inline void printInt(const int& num) {
    if (num < 10) {
      putchar(num + '0');
      return;
    }
    printInt(num / 10);
    putchar((num % 10) + '0');
  }
  inline void printINT(const long long& num) {
    if (num < 10) {
      putchar(num + '0');
      return;
    }
    printINT(num / 10);
    putchar((num % 10) + '0');
  }
  inline fastIO operator<<(const int& num) {
    if (num < 0)
      putchar('-'), printInt(-num);
    else
      printInt(num);
    return *this;
  }
  inline fastIO operator<<(const long long& num) {
    if (num < 0)
      putchar('-'), printINT(-num);
    else
      printINT(num);
    return *this;
  }
  inline fastIO operator<<(const float& num) {
    printf("%.10f", num);
    return *this;
  }
  inline fastIO operator<<(const double& num) {
    printf("%.16lf", num);
    return *this;
  }
  inline fastIO operator<<(const long double& num) {
    printf("%.20Lf", num);
    return *this;
  }
  inline fastIO operator<<(const char& num) {
    putchar(num);
    return *this;
  }
  inline fastIO operator<<(const char* num) {
    for (int i = 0; num[i]; i++) putchar(num[i]);
    return *this;
  }
  inline fastIO operator<<(const string& num) {
    cout << num;
    return *this;
  }
} fio;
int n, m;
char s[25][25];
int a[25][25];
int dp[(1 << (21))];
int msk[25][35], mx[25][35], sum[25][35];
int main() {
  fio >> n >> m;
  for (int i = 0; i < n; i++) {
    fio >> s[i];
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      fio >> a[i][j];
    }
  }
  for (int i = 0; i < m; i++) {
    for (int j = 0; j < n; j++) {
      int c = s[j][i] - 'a';
      msk[i][c] |= (1 << (j));
      mx[i][c] = max(mx[i][c], a[j][i]);
      sum[i][c] += a[j][i];
    }
  }
  memset((void*)dp, 0x3f, sizeof(dp));
  dp[0] = 0;
  for (int i = 0; i < (1 << (n)) - 1; i++) {
    if (dp[i] == ((int)0x3f3f3f3f)) {
      continue;
    }
    int f = __builtin_ctz(~i);
    for (int j = 0; j < m; j++) {
      int c = s[f][j] - 'a';
      dp[i | (1 << (f))] = min(dp[i | (1 << (f))], dp[i] + a[f][j]);
      dp[i | msk[j][c]] = min(dp[i | msk[j][c]], dp[i] + sum[j][c] - mx[j][c]);
    }
  }
  fio << dp[(1 << (n)) - 1] << '\n';
  return 0;
}
