#include <bits/stdc++.h>
using namespace std;
const int N = 501;
int dp[N][N][2];
char a[N][N];
const int MOD = 1e9 + 7;
void add(int &a, int b) {
  a += b;
  if (a >= MOD) a -= MOD;
  if (a < 0) a += MOD;
}
int mul(int a, int b) { return (long long)a * b % MOD; }
int power(int a, int b) {
  int ans = 1;
  while (b > 0) {
    if (b & 1) ans = mul(ans, a);
    a = mul(a, a);
    b >>= 1;
  }
  return ans;
}
int main() {
  int n, m;
  cin >> n >> m;
  for (int i = 1; i <= n; i++) {
    cin >> (a[i] + 1);
  }
  for (int x2 = 1; x2 <= n; x2++) {
    for (int x1 = n; x1 >= 1; x1--) {
      for (int y1 = m; y1 >= 1; y1--) {
        int x2cc = x2 % 2;
        int y2 = n + m - x2 - x1 - y1 + 2;
        dp[x1][y1][x2cc] = 0;
        if (x1 > x2 || y1 > y2) continue;
        if (y2 < 1 || y2 > m) continue;
        if (x1 == x2 && y1 == y2) {
          dp[x1][y1][x2cc] = 1;
          continue;
        }
        if ((x2 == x1 + 1 && y1 == y2) || (x1 == x2 && y2 == y1 + 1))
          if (a[x1][y1] == a[x2][y2]) {
            dp[x1][y1][x2cc] = 1;
            continue;
          }
        if (x1 < n) {
          if (x2 > 1)
            if (a[x1 + 1][y1] == a[x2 - 1][y2])
              add(dp[x1][y1][x2cc], dp[x1 + 1][y1][!x2cc]);
          if (y2 > 1)
            if (a[x1 + 1][y1] == a[x2][y2 - 1])
              add(dp[x1][y1][x2cc], dp[x1 + 1][y1][x2cc]);
        }
        if (y1 < m) {
          if (x2 > 1)
            if (a[x1][y1 + 1] == a[x2 - 1][y2])
              add(dp[x1][y1][x2cc], dp[x1][y1 + 1][!x2cc]);
          if (y2 > 1)
            if (a[x1][y1 + 1] == a[x2][y2 - 1])
              add(dp[x1][y1][x2cc], dp[x1][y1 + 1][x2cc]);
        }
      }
    }
  }
  if (a[1][1] != a[n][m]) dp[1][1][n % 2] = 0;
  cout << dp[1][1][n % 2] << endl;
}
