#include <bits/stdc++.h>
using namespace std;
long long int m, n;
string str[505];
long long int dp[2][506][506] = {{{0}}};
bool ok(long long int r1, long long int c1, long long int r2, long long int c2);
void trell() {
  for (int i = 0; i <= (n + m - 2) / 2; i++) {
    for (int j = 0; j < m; j++) {
      for (int k = 0; k < m; k++) {
        cout << dp[i][j][k] << " ";
      }
      cout << "\n";
    }
    cout << "\n";
  }
}
int main() {
  cin >> m >> n;
  for (long long int i = 0; i < m; i++) {
    cin >> str[i];
  }
  dp[1][0][m - 1] = 1;
  for (long long int moves = 0; moves < ((n + m - 2) / 2); moves++) {
    for (long long int i = 0; i < m; i++)
      for (long long int j = 0; j < m; j++)
        dp[0][i][j] = dp[1][i][j], dp[1][i][j] = 0;
    for (long long int r1 = 0; r1 < m; r1++) {
      for (long long int r2 = 0; r2 < m; r2++) {
        long long int c1 = moves - r1;
        long long int c2 = -r2 + n + m - moves - 2;
        if (!ok(r1, c1, r2, c2)) continue;
        if (str[r1][c1] != str[r2][c2]) continue;
        long long int yahan_tak = dp[0][r1][r2];
        if (ok(r1 + 1, c1, r2, c2 - 1) && str[r1 + 1][c1] == str[r2][c2 - 1])
          dp[1][r1 + 1][r2] = (dp[1][r1 + 1][r2] + yahan_tak) % 1000000007;
        if (ok(r1 + 1, c1, r2 - 1, c2) && str[r1 + 1][c1] == str[r2 - 1][c2])
          dp[1][r1 + 1][r2 - 1] =
              (dp[1][r1 + 1][r2 - 1] + yahan_tak) % 1000000007;
        if (ok(r1, c1 + 1, r2 - 1, c2) && str[r1][c1 + 1] == str[r2 - 1][c2])
          dp[1][r1][r2 - 1] = (dp[1][r1][r2 - 1] + yahan_tak) % 1000000007;
        if (ok(r1, c1 + 1, r2, c2 - 1) && str[r1][c1 + 1] == str[r2][c2 - 1])
          dp[1][r1][r2] = (dp[1][r1][r2] + yahan_tak) % 1000000007;
      }
    }
  }
  int ans = 0;
  for (long long int i = 0; i < m; i++) {
    for (long long int j = 0; j < m; j++) {
      ans = (ans + dp[1][i][j]) % 1000000007;
    }
  }
  cout << ans;
  return 0;
}
bool ok(long long int r1, long long int c1, long long int r2,
        long long int c2) {
  if (r1 >= 0 && r2 < m && c1 >= 0 && c2 < n && r1 < m && r2 >= 0 && c1 < n &&
      c2 >= 0 && r1 <= r2 && c1 <= c2)
    return true;
  return false;
}
