#include <bits/stdc++.h>
template <class T>
T abs(T x) {
  return (x > 0) ? x : (-x);
}
int n, m, f[2][510][510], mid, res = 0;
char b[510][510];
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; ++i) scanf("%s", &b[i][1]);
  if (b[1][1] != b[n][m]) {
    printf("0\n");
    return 0;
  }
  f[1][1][n] = 1;
  mid = (n + m) >> 1;
  for (int i = 2; i <= mid; ++i) {
    for (int j = 1; j <= n; ++j)
      for (int k = 1; k <= n; ++k) f[i & 1][j][k] = 0;
    for (int j = 1; j <= std::min(i, n); ++j) {
      if (i + 1 - j > m) continue;
      for (int k = 1; k <= n; ++k) {
        if (k < n + 1 - i || k > m + n - i) continue;
        if (b[j][i + 1 - j] == b[k][m + n + 1 - k - i]) {
          f[i & 1][j][k] =
              ((f[(i - 1) & 1][j][k] + f[(i - 1) & 1][j - 1][k]) % 1000000007 +
               (f[(i - 1) & 1][j][k + 1] + f[(i - 1) & 1][j - 1][k + 1]) %
                   1000000007) %
              1000000007;
        }
      }
    }
  }
  if ((n + m) & 1) {
    for (int j = 1; j <= std::min(mid, n); ++j) {
      if (mid + 1 - j < m && b[j][mid + 1 - j] == b[j][mid + 2 - j])
        res = (res + f[mid & 1][j][j]) % 1000000007;
      if (j < n && b[j][mid + 1 - j] == b[j + 1][mid + 1 - j])
        res = (res + f[mid & 1][j][j + 1]) % 1000000007;
    }
  } else {
    for (int j = 1; j <= std::min(mid, n); ++j) {
      if (mid + 1 - j > m) continue;
      res = (res + f[mid & 1][j][j]) % 1000000007;
    }
  }
  printf("%d\n", res);
  return 0;
}
