func_code_string: #include <bits/stdc++.h>   #pragma GCC optimize(3,  Ofast ,  inline )   #pragma GCC target( avx,avx2 )   using namespace std;   template <class t>   inline t read(t &x) {     char c = getchar();     bool f = 0;     x = 0;     while (!isdigit(c)) f |= c ==  - , c = getchar();     while (isdigit(c)) x = (x << 1) + (x << 3) + (c ^ 48), c = getchar();     if (f) x = -x;     return x;   }   template <class t>   inline void write(t x) {     if (x < 0)       putchar( - ), write(-x);     else {       if (x > 9) write(x / 10);       putchar( 0  + x % 10);     }   }   const long long N = 1005, mod = 1e9 + 7;   long long f[N][N][2][2], g[N], ans[N], n, m, fac[N], inv[N];   long long C(long long n, long long m) {     return fac[n] * inv[m] % mod * inv[n - m] % mod;   }   signed main() {     read(n);     read(m);     fac[0] = inv[0] = inv[1] = 1;     for (long long i = 1; i <= n; i++) fac[i] = fac[i - 1] * i % mod;     for (long long i = 2; i <= n; i++)       inv[i] = inv[mod % i] * (mod - mod / i) % mod;     for (long long i = 1; i <= n; i++) inv[i] = inv[i] * inv[i - 1] % mod;     f[1][0][0][0] = f[1][1][0][1] = 1;     for (long long i = 2; i <= n; i++)       for (long long j = 0; j < i; j++) {         f[i][j][0][0] =             (f[i][j][0][0] + f[i - 1][j][0][0] + f[i - 1][j][1][0]) % mod;         f[i][j][1][0] =             (f[i][j][1][0] + f[i - 1][j][0][1] + f[i - 1][j][1][1]) % mod;         f[i][j + 1][0][0] = f[i - 1][j][0][0];         f[i][j + 1][0][1] = (f[i - 1][j][0][0] + f[i - 1][j][1][0]) % mod;         f[i][j + 1][1][0] = f[i - 1][j][0][1];         f[i][j + 1][1][1] = (f[i - 1][j][0][1] + f[i - 1][j][1][1]) % mod;       }     for (long long i = 0; i <= n; i++)       g[i] = (f[n][i][0][0] + f[n][i][1][0]) * fac[n - i] % mod;     for (long long i = 0; i <= n; i++)       for (long long j = i, op = 1; j <= n; j++, op *= -1)         ans[i] = (ans[i] + mod + op * C(j, i) * g[j] % mod) % mod;     write(ans[m]);   }   