#include #include using namespace std; using namespace atcoder; #define rep(i, n) REP(i, 0, n) #define REP(i, s, e) for (int i = (s); i < (int)(e); i++) #define repr(i, n) REPR(i, n, 0) #define REPR(i, s, e) for (int i = (int)(s - 1); i >= (int)(e); i--) #define all(r) r.begin(), r.end() #define rall(r) r.rbegin(), r.rend() typedef long long ll; typedef vector vi; typedef vector vl; template T chmax(T& a, const U& b) { if (a >= b) return false; a = b; return true; } template T chmin(T& a, const U& b) { if (a <= b) return false; a = b; return true; } void yes_no(bool f, string yes = "Yes", string no = "No") { cout << (f ? yes : no) << "\n"; } void solve() { int n; cin >> n; if (n <= 2) { cout << n << "\n"; return; } using mint = modint1000000007; vector dp(n + 1, vector(n + 1, vector(2, vector(2, mint(0))))); dp[2][0][0][0] = 2; REP(i, 1, n) rep(ng, i) { { mint tmp = dp[i][ng][1][1]; if (ng > 0) dp[i + 1][ng - 1][0][0] += tmp; dp[i + 1][ng][1][1] += tmp; dp[i + 1][ng + 1][1][1] += tmp; if (ng > 0) dp[i + 1][ng - 1][1][0] += tmp * (ng - 2); dp[i + 1][ng][1][0] += tmp * (i - ng); } { mint tmp = dp[i][ng][1][0]; dp[i + 1][ng][0][1] += tmp; dp[i + 1][ng + 1][0][1] += tmp; if (ng > 0) dp[i + 1][ng - 1][0][0] += tmp * (ng - 1); dp[i + 1][ng][0][0] += tmp * (i - ng); } { mint tmp = dp[i][ng][0][1]; if (ng > 0) dp[i + 1][ng - 1][0][0] += tmp; dp[i + 1][ng + 1][1][1] += tmp * 2; if (ng > 0) dp[i + 1][ng - 1][1][0] += tmp * (ng - 1); dp[i + 1][ng][1][0] += tmp * (i - ng - 1); } { mint tmp = dp[i][ng][0][0]; dp[i + 1][ng + 1][0][1] += tmp * 2; if (ng > 0) dp[i + 1][ng - 1][0][0] += tmp * ng; dp[i + 1][ng][0][0] += tmp * (i - ng - 1); } } mint ans = dp[n][0][0][0]; cout << ans.val() << "\n"; } int main() { cin.tie(0); ios::sync_with_stdio(false); int t = 1; // cin >> t; rep(ti, t) solve(); return 0; }