#include #define REP_(i, a_, b_, a, b, ...) \ for (int i = (a), END_##i = (b); i < END_##i; ++i) #define REP(i, ...) REP_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__) #define ALL(x) std::begin(x), std::end(x) using i64 = long long; #include using Mint = atcoder::modint1000000007; std::ostream &operator<<(std::ostream &os, const Mint &m) { return os << m.val(); } template inline bool chmax(T &a, U b) { return a < b and ((a = std::move(b)), true); } template inline bool chmin(T &a, U b) { return a > b and ((a = std::move(b)), true); } template inline int ssize(const T &a) { return (int) std::size(a); } template std::istream &operator>>(std::istream &is, std::vector &a) { for (auto &x : a) is >> x; return is; } template std::ostream &operator<<(std::ostream &os, const std::pair &a) { return os << "(" << a.first << ", " << a.second << ")"; } template std::ostream &print_seq(const Container &a, std::string_view sep = " ", std::string_view ends = "\n", std::ostream &os = std::cout) { auto b = std::begin(a), e = std::end(a); for (auto it = std::begin(a); it != e; ++it) { if (it != b) os << sep; os << *it; } return os << ends; } template struct is_iterable : std::false_type {}; template struct is_iterable())), decltype(std::end(std::declval()))>> : std::true_type { }; template::value && !std::is_same::value && !std::is_same::value>> std::ostream &operator<<(std::ostream &os, const T &a) { return print_seq(a, ", ", "", (os << "{")) << "}"; } void print() { std::cout << "\n"; } template void print(const T &x) { std::cout << x << "\n"; } template void print(const Head &head, Tail... tail) { std::cout << head << " "; print(tail...); } void read_from_cin() {} template void read_from_cin(T &value, Ts &...args) { std::cin >> value; read_from_cin(args...); } #define INPUT(type, ...) \ type __VA_ARGS__; \ read_from_cin(__VA_ARGS__) #ifdef MY_DEBUG #include "debug_dump.hpp" #else #define DUMP(...) #endif using namespace std; auto solve() -> Mint { INPUT(int, n); if (n == 1) return 1; const int L = n + 10; auto dp = vector(n, vector(L, vector(2, vector(2, Mint(0))))); dp[1][0][0][0] = 2; REP(i, 2, n) { int slots = i + 1; // number of insertion points REP(j, L) { // due if (j > slots) break; REP(p1, 2) { REP(p2, 2) { auto f = dp[i - 1][j][p1][p2]; if (f.val() == 0) continue; if (p1 == 0 and p2 == 0) { if (j + 1 < L) dp[i][j + 1][1][0] += f * 2; if (j - 1 >= 0) dp[i][j - 1][0][0] += f * j; if (slots - 2 - j > 0) dp[i][j][0][0] += f * (slots - 2 - j); } else if (p1 == 0 and p2 == 1) { if (j + 1 <= n) dp[i][j + 1][1][0] += f; dp[i][j][1][0] += f; if (j - 1 >= 0) dp[i][j - 1][0][0] += f * (j - 1); if (slots - 1 - j > 0) dp[i][j][0][0] += f * (slots - 1 - j); } else if (p1 == 1 and p2 == 0) { if (j + 1 < L) dp[i][j + 1][1][1] += f * 2; if (j - 1 >= 0) dp[i][j - 1][0][0] += f; if (j - 1 >= 0) dp[i][j - 1][0][1] += f * (j - 1); if (slots - 2 - j > 0) dp[i][j][0][1] += f * (slots - 2 - j); } else { if (j + 1 < L) dp[i][j + 1][1][1] += f; dp[i][j][1][1] += f; if (j - 1 >= 0) dp[i][j - 1][0][0] += f; if (j - 1 >= 0) dp[i][j - 1][0][1] += f * (j - 2); if (slots - 1 - j > 0) dp[i][j][0][1] += f * (slots - 1 - j); } } } } } Mint ans = dp[n - 1][0][0][0]; return ans; } int main() { ios_base::sync_with_stdio(false), cin.tie(nullptr); int t = 1; REP(test_case, t) { auto ans = solve(); print(ans); } }