#include <bits/stdc++.h>
using std::memset;
char s[510][510];
int f[2][510][510], ans, n, m;
const int P = 1e9 + 7;
inline bool pd(int x, int y, int xx, int yy) {
  if (x == xx && y == yy) return 1;
  if (x == xx && y + 1 == yy) return 1;
  if (x + 1 == xx && y == yy) return 1;
  return 0;
}
int main() {
  scanf("%d%d", &n, &m);
  for (register int i = 1; i <= n; i++) scanf("%s", s[i] + 1);
  if (s[1][1] == s[n][m])
    f[1][1][n] = 1;
  else {
    puts("0");
    return 0;
  }
  for (register int i = 1; i <= n; i++) {
    for (register int j = 1; 2 * (i + j) <= m + n + 2; j++)
      for (register int k = n; k >= i; k--)
        if (s[i][j] == s[k][n + m - k - i - j + 2]) {
          f[i & 1][j][k] = (f[i & 1][j][k] + f[i & 1][j - 1][k]) % P;
          f[i & 1][j][k] = (f[i & 1][j][k] + f[(i + 1) & 1][j][k]) % P;
          f[i & 1][j][k] = (f[i & 1][j][k] + f[i & 1][j - 1][k + 1]) % P;
          f[i & 1][j][k] = (f[i & 1][j][k] + f[(i + 1) & 1][j][k + 1]) % P;
          if (pd(i, j, k, n + m - k - i - j + 2))
            ans = (ans + f[i & 1][j][k]) % P;
        }
    memset(f[(i + 1) & 1], 0, sizeof(f[(i + 1) & 1]));
  }
  printf("%d", ans);
}
