#include <bits/stdc++.h>
using namespace std;
const int module = 1000000007;
string A[510];
int F[2][510][510];
int m, n;
inline bool valid(int x, int y) { return 0 < x && x <= m && 0 < y && y <= n; }
inline bool valid(int x, int y, int u, int v) {
  return valid(x, y) && valid(u, v) && A[x][y] == A[u][v];
}
inline void add(int &s, int x) { s = (s + x) % module; }
void enter() {
  cin >> m >> n;
  for (int i = 1; i <= m; ++i) cin >> A[i], A[i] = " " + A[i];
}
void solve() {
  if (A[1][1] != A[m][n]) {
    cout << 0;
    return;
  }
  F[1][1][m] = 1;
  int res = 0;
  for (int i = 1, k = 1; i <= m; ++i, k ^= 1)
    for (int j = 1; j <= n; ++j)
      if (i != 1 || j != 1)
        for (int x = 1; x <= m; ++x) {
          int y = m + n - x - i - j + 2;
          if (!valid(i, j, x, y)) continue;
          int s = 0;
          if (valid(i, j - 1, x, y + 1)) add(s, F[k][j - 1][x]);
          if (valid(i - 1, j, x, y + 1)) add(s, F[k ^ 1][j][x]);
          if (valid(i, j - 1, x + 1, y)) add(s, F[k][j - 1][x + 1]);
          if (valid(i - 1, j, x + 1, y)) add(s, F[k ^ 1][j][x + 1]);
          F[k][j][x] = s;
          if ((i == x && j == y) || (i + 1 == x && j == y) ||
              (i == x && j + 1 == y))
            add(res, F[k][j][x]);
        }
  cout << res;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  if (ifstream("test.inp")) cin.rdbuf((new ifstream("test.inp"))->rdbuf());
  enter();
  solve();
}
