#include <bits/stdc++.h>
using namespace std;
int n, m;
char s[505][505];
long long dp[2][505][505];
long long ans;
const long long mod = 1e9 + 7;
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; ++i) scanf("%s", s[i] + 1);
  dp[0][1][n] = 1;
  for (int x = 2; x <= (n + m) / 2 + 1; ++x) {
    int y = n + m - x + 2;
    memset(dp[1], 0, sizeof(dp[1]));
    for (int i = 1; i <= n; ++i)
      for (int p = i; p <= n; ++p) {
        int j = x - i, q = y - p;
        if (j < 1 || j > m || q < 1 || q > m || j > q) continue;
        if (s[i][j] != s[p][q])
          dp[1][i][p] = 0;
        else
          dp[1][i][p] = (dp[0][i - 1][p] + dp[0][i - 1][p + 1] + dp[0][i][p] +
                         dp[0][i][p + 1]) %
                        mod;
      }
    for (int i = 1; i <= n; ++i)
      for (int j = 1; j <= n; ++j) dp[0][i][j] = dp[1][i][j];
  }
  for (int i = 1; i <= n; ++i)
    for (int j = 1; j <= n; ++j) ans += dp[0][i][j], ans %= mod;
  printf("%I64d\n", ans);
  return 0;
}
