func_code_string: #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;   }   