#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,inline")
#pragma GCC target( \
    "sse,sse2,sse3,ssse3,sse4,sse4.1,sse4.2,popcnt,abm,mmx,avx,avx2,tune=native")
#pragma GCC optimize(1)
#pragma G++ optimize(1)
#pragma GCC optimize(2)
#pragma G++ optimize(2)
#pragma GCC optimize(3)
#pragma G++ optimize(3)
#pragma GCC optimize("-funsafe-loop-optimizations")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-fwhole-program")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-falign-functions")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fcse-follow-jumps")
#pragma GCC optimize("-fcse-skip-blocks")
#pragma GCC optimize("-fdelete-null-pointer-checks")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-finline-small-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-freorder-blocks")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("-fsched-interblock")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("-fschedule-insns")
#pragma GCC optimize("-fschedule-insns2")
#pragma GCC optimize("-fstrict-aliasing")
#pragma GCC optimize("-fstrict-overflow")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
using namespace std;
inline void rdl(long long &val) {
  long long x = 0;
  int f = 1;
  char ch = getchar();
  while ((ch < '0' or ch > '9') and ch != '-') ch = getchar();
  if (ch == '-') {
    f = -1;
    ch = getchar();
  }
  while (ch >= '0' and ch <= '9') {
    x = (x << 3) + (x << 1) + ch - '0';
    ch = getchar();
  }
  val = x * f;
}
inline void rdi(int &val) {
  int x = 0;
  int f = 1;
  char ch = getchar();
  while ((ch < '0' or ch > '9') and ch != '-') ch = getchar();
  if (ch == '-') {
    f = -1;
    ch = getchar();
  }
  while (ch >= '0' and ch <= '9') {
    x = (x << 3) + (x << 1) + ch - '0';
    ch = getchar();
  }
  val = x * f;
}
inline long long rdl() {
  long long x = 0;
  int f = 1;
  char ch = getchar();
  while ((ch < '0' or ch > '9') and ch != '-') ch = getchar();
  if (ch == '-') {
    f = -1;
    ch = getchar();
  }
  while (ch >= '0' and ch <= '9') {
    x = (x << 3) + (x << 1) + ch - '0';
    ch = getchar();
  }
  return x * f;
}
inline int rdi() {
  int x = 0;
  int f = 1;
  char ch = getchar();
  while ((ch < '0' or ch > '9') and ch != '-') ch = getchar();
  if (ch == '-') {
    f = -1;
    ch = getchar();
  }
  while (ch >= '0' and ch <= '9') {
    x = (x << 3) + (x << 1) + ch - '0';
    ch = getchar();
  }
  return x * f;
}
inline void write(int x) {
  if (x < 0) putchar('-'), x = -x;
  if (x > 9) write(x / 10);
  putchar(x % 10 + '0');
}
inline void _write(int x) {
  write(x);
  putchar(' ');
}
inline void print(int x) {
  write(x);
  putchar('\n');
}
inline void write(long long x) {
  if (x < 0) putchar('-'), x = -x;
  if (x > 9) write(x / 10);
  putchar(x % 10 + '0');
}
inline void _write(long long x) {
  write(x);
  putchar(' ');
}
inline void print(long long x) {
  write(x);
  putchar('\n');
}
const int mxn = 21;
int a[mxn][mxn], N, M, dp[1 << mxn], l, n, m, t, h, b, c;
char s[mxn][10 * mxn];
int main() {
  int i, j;
  scanf("%d%d", &N, &M);
  for (i = 0; i < N; ++i) scanf("%s", s[i]);
  for (i = 0; i < N; ++i)
    for (j = 0; j < M; ++j) scanf("%d", &a[i][j]);
  memset(dp, 63, sizeof(dp));
  dp[0] = 0;
  for (m = 0; m < (1 << N); ++m) {
    for (b = 0; b < N; ++b)
      if (!(m & (1 << b))) {
        l = b;
        break;
      }
    for (c = 0; c < M; ++c) {
      dp[m + (1 << l)] = min(dp[m + (1 << l)], dp[m] + a[l][c]);
      n = m, t = 0, h = 0;
      for (i = 0; i < N; ++i)
        if (s[i][c] == s[l][c])
          n |= (1 << i), t += a[i][c], h = max(h, a[i][c]);
      dp[n] = min(dp[n], dp[m] + t - h);
    }
  }
  printf("%d\n", dp[(1 << N) - 1]);
  return 0;
}
