#include <bits/stdc++.h>
using namespace std;
const int maxn = 510;
const int mod = 1e9 + 7;
int n, m;
char s[maxn][maxn];
long long dp[2][maxn][maxn];
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) {
    scanf("%s", s[i] + 1);
  }
  if (s[1][1] != s[n][m]) {
    puts("0");
    return 0;
  }
  int mid = (n + m) >> 1, e = 0;
  dp[0][1][n] = 1;
  for (int num = 2; num <= mid; num++) {
    e ^= 1;
    memset(dp[e], 0, sizeof dp[e]);
    for (int i = 1; i <= min(num, n); i++) {
      int j = num + 1 - i;
      for (int k = n; k >= max(n - num, i); k--) {
        int l = m - num + n - k + 1;
        if (s[i][j] != s[k][l]) continue;
        dp[e][i][k] = (dp[e][i][k] + dp[e ^ 1][i][k]) % mod;
        dp[e][i][k] = (dp[e][i][k] + dp[e ^ 1][i - 1][k]) % mod;
        dp[e][i][k] = (dp[e][i][k] + dp[e ^ 1][i][k + 1]) % mod;
        dp[e][i][k] = (dp[e][i][k] + dp[e ^ 1][i - 1][k + 1]) % mod;
      }
    }
  }
  long long ans = 0;
  for (int i = 1; i <= n; i++) {
    ans = (ans + dp[e][i][i] + ((n + m) & 1) * dp[e][i][i + 1]) % mod;
  }
  printf("%lld\n", ans);
  return 0;
}
