#include #define GET_MACRO(a, b, c, NAME, ...) NAME #define rep(...) GET_MACRO(__VA_ARGS__, rep3, rep2)(__VA_ARGS__) #define rep2(i, a) rep3 (i, 0, a) #define rep3(i, a, b) for (int i = (a); i < (b); i++) #define repr(...) GET_MACRO(__VA_ARGS__, repr3, repr2)(__VA_ARGS__) #define repr2(i, a) repr3 (i, 0, a) #define repr3(i, a, b) for (int i = (b) - 1; i >= (a); i--) #define chmin(a, b) ((b) < a && (a = (b), true)) #define chmax(a, b) (a < (b) && (a = (b), true)) using namespace std; typedef long long ll; const ll mod = 1e9 + 7; ll dp[1010][1010][2][2]; // pos, bad, (n-3, n-1), (n-2, n) int main() { int n; cin >> n; dp[0][0][0][0] = 1; rep (i, n) rep (j, n + 1) rep (k, 2) rep (l, 2) { ll v = dp[i][j][k][l]; int way = i + 1; if (k) { // n-3,(n+1),n-1 (dp[i + 1][j][l][true] += v) %= mod; // (n+1),n-1,n-3 (dp[i + 1][j + k][l][true] += v) %= mod; way -= 2; } else { if (i >= 2) { // (n+1),n-1 or n-1,(n+1) (dp[i + 1][j + k][l][true] += v * 2) %= mod; way -= 2; } } // n-2, (n+1), n if (l) { (dp[i + 1][j + k][false][false] += v) %= mod; way -= 1; } (dp[i + 1][j - 1 + k][l][false] += v * j % mod) %= mod; way -= j; (dp[i + 1][j + k][l][false] += v * way % mod) %= mod; } cout << dp[n][0][0][0] << endl; }