#include <bits/stdc++.h>
using namespace std;
bool isprime(long long n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (long long i = 5; i * i <= n; i += 6) {
    if (n % i == 0 || n % (i + 2) == 0) return false;
  }
  return true;
}
long long modexp(long long a, long long b, long long m) {
  long long r = 1;
  a = a % m;
  while (b > 0) {
    if (b & 1) r = (r * a) % m;
    b = b >> 1;
    a = (a * a) % m;
  }
  return r % m;
}
long long builtin_popcount(long long x) {
  long long cnt = 0;
  for (long long i = 60; i >= 0; i--) {
    if ((1LL << i) & x) cnt++;
  }
  return cnt;
}
long long addmod(long long a, long long b) {
  a %= 1000000007;
  b %= 1000000007;
  return (a + b) % 1000000007;
}
long long mulmod(long long a, long long b) {
  a %= 1000000007;
  b %= 1000000007;
  return (a * b) % 1000000007;
}
long long submod(long long a, long long b) {
  a %= 1000000007;
  b %= 1000000007;
  a -= b;
  if (a < 0) a += 1000000007;
  return a % 1000000007;
}
struct CustomCompare {
  bool operator()(long long a, long long b) { return a > b; }
};
const int mxn = 501, mxm = 251;
int dp[mxn][mxn][mxm];
char grid[mxn][mxn];
int n, m;
int solve(int x1, int x2, int moves) {
  int y1 = 1 + (moves - (x1 - 1));
  int y2 = m - (moves - (n - x2));
  if (x1 > x2 || y1 > y2 || grid[x1][y1] != grid[x2][y2]) return 0;
  if (x1 == x2 && y2 - y1 <= 1) return 1;
  if (y1 == y2 && x2 - x1 <= 1) return 1;
  int ans = dp[x1][x2][moves];
  if (ans != -1) return ans;
  ans = 0;
  ans = addmod(ans, solve(x1 + 1, x2, moves + 1));
  ans = addmod(ans, solve(x1 + 1, x2 - 1, moves + 1));
  ans = addmod(ans, solve(x1, x2, moves + 1));
  ans = addmod(ans, solve(x1, x2 - 1, moves + 1));
  return dp[x1][x2][moves] = ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  memset(dp, -1, sizeof(dp));
  cin >> n >> m;
  for (int i = 1; i < n + 1; i++) {
    for (int j = 1; j < m + 1; j++) cin >> grid[i][j];
  }
  cout << solve(1, n, 0) << endl;
  return 0;
}
