#pragma comment(linker, "/stack:200000000") #pragma GCC optimize("Ofast") #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native") // need #include #include // data structure #include #include #include #include #include #include #include #include #include //#include #include #include #include #include // stream //#include #include //#include #include // etc #include #include #include #include #include #include #include // input #define INIT std::ios::sync_with_stdio(false);std::cin.tie(0); #define VAR(type, ...)type __VA_ARGS__;MACRO_VAR_Scan(__VA_ARGS__); template void MACRO_VAR_Scan(T& t) { std::cin >> t; } templatevoid MACRO_VAR_Scan(First& first, Rest& ...rest) { std::cin >> first; MACRO_VAR_Scan(rest...); } #define VEC_ROW(type, n, ...)std::vector __VA_ARGS__;MACRO_VEC_ROW_Init(n, __VA_ARGS__); for(int w_=0; w_ void MACRO_VEC_ROW_Init(int n, T& t) { t.resize(n); } templatevoid MACRO_VEC_ROW_Init(int n, First& first, Rest& ...rest) { first.resize(n); MACRO_VEC_ROW_Init(n, rest...); } template void MACRO_VEC_ROW_Scan(int p, T& t) { std::cin >> t[p]; } templatevoid MACRO_VEC_ROW_Scan(int p, First& first, Rest& ...rest) { std::cin >> first[p]; MACRO_VEC_ROW_Scan(p, rest...); } #define VEC(type, c, n) std::vector c(n);for(auto& i:c)std::cin>>i; #define MAT(type, c, m, n) std::vector> c(m, std::vector(n));for(auto& R:c)for(auto& w:R)std::cin>>w; // output #define OUT(dist) std::cout<<(dist); #define FOUT(n, dist) std::cout<=(a);--w) #define REP(w, n) for(int w=0;w=0;--w) #define IN(a, x, b) (a<=x && x inline T CHMAX(T & a, const T b) { return a = (a < b) ? b : a; } template inline T CHMIN(T& a, const T b) { return a = (a > b) ? b : a; } #define EXCEPTION(msg) throw std::string("Exception : " msg " [ in ") + __func__ + " : " + std::to_string(__LINE__) + " lines ]" #define TRY(cond, msg) try {if (cond) EXCEPTION(msg);}catch (std::string s) {std::cerr << s << std::endl;} //void CHECKTIME(std::function f) { auto start = std::chrono::system_clock::now(); f(); auto end = std::chrono::system_clock::now(); auto res = std::chrono::duration_cast((end - start)).count(); std::cerr << "[Time:" << res << "ns (" << res / (1.0e9) << "s)]\n"; } // test template using V = std::vector; template using VV = V>; template std::ostream& operator<<(std::ostream& os, std::pair p) { os << "(" << p.first << ", " << p.second << ")"; return os; } #define random_shuffle "USE std::shuffle!"; // type/const #define int ll using ll = long long; using ull = unsigned long long; using ld = long double; using PAIR = std::pair; using PAIRLL = std::pair; constexpr int INFINT = (1 << 30) - 1; // 1.07x10^ 9 constexpr int INFINT_LIM = (1LL << 31) - 1; // 2.15x10^ 9 constexpr ll INFLL = 1LL << 60; // 1.15x10^18 constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62); // 9.22x10^18 constexpr double EPS = 1e-10; constexpr int MOD = 1000000007; constexpr double PI = 3.141592653589793238462643383279; template void FILL(T(&a)[N], const T & val) { for (auto& x : a) x = val; } template void FILL(ARY(&a)[N][M], const T & val) { for (auto& b : a) FILL(b, val); } template void FILL(std::vector & a, const T & val) { for (auto& x : a) x = val; } template void FILL(std::vector> & a, const T & val) { for (auto& b : a) FILL(b, val); } // ------------>8------------------------------------->8------------ ll powMod(ll n, ll p, ll mod) { ll res = 1; while (p) { if (p & 1) (res *= n) %= mod; (n *= n) %= mod; p >>= 1; } return res; } ll invMod(ll n, ll mod) { return powMod(n, MOD - 2, MOD); } const signed FACT_MAX_N = 1000006; signed fact[FACT_MAX_N]; signed factInv[FACT_MAX_N]; struct INIT_FACT { INIT_FACT() { fact[0] = 1; for (int i = 1; i < FACT_MAX_N; ++i) fact[i] = (long long)i * fact[i - 1] % MOD; factInv[FACT_MAX_N - 1] = powMod(fact[FACT_MAX_N - 1], MOD - 2, MOD); for (int i = FACT_MAX_N - 2; i >= 0; --i) factInv[i] = (long long)(i + 1) * factInv[i + 1] % MOD; } } init_fact; #if true // true if use MOD /* n,r<=10^6, query O(1)*/ ll Permutation(int n, int r) { if (r == 0) return 1; if (n < r) return 0; return (long long)fact[n] * factInv[n - r] % MOD; } ll Combination(int n, int r) { if (r == 0) return 1; if (n < r) return 0; return (long long)fact[n] * factInv[n - r] % MOD * factInv[r] % MOD; } ll CombinationWithRepetition(ll n, ll r) { return Combination(n + r - 1, r); } /*n<=10^9, r<=10^5, query O(r)*/ /*ll Combination(ll n, ll r, ll mod) { if (n < r) return 0; ll ans = 1; if (n < 2 * r) r = n - r; for (int i = 1; i <= r; ++i) { ans *= n - i + 1; ans %= mod; ans *= powMod(i, mod - 2, mod); ans %= mod; } return ans; } ll Permutation(int n, int r, int mod) { return Combination(n, r, mod) * fact[r] % MOD; }*/ #else // unuse MOD const signed COMB_MAX_N = 67; // <- max : 67 long long comb[COMB_MAX_N][COMB_MAX_N]; struct INIT_COMB { INIT_COMB() { for (int i = 0; i < COMB_MAX_N; ++i) { for (int j = 0; j <= i; ++j) { if (j == 0 || j == i) comb[i][j] = 1; else comb[i][j] = comb[i - 1][j - 1] + comb[i - 1][j]; } } } } init_comb; #endif signed main() { INIT; VAR(int, n); VEC_ROW(int, n - 1, a, b); std::vector> g(n); REP(i, n-1) { --a[i]; --b[i]; g[a[i]].emplace_back(b[i]); g[b[i]].emplace_back(a[i]); } V depth(n, 0); auto rec = [&](auto && f, int v, int par) -> void { for (auto& to : g[v]) if (to != par) { depth[to] = depth[v] + 1; f(f, to, v); } }; rec(rec, 0, -1); int ans = 0; for (auto& d : depth) { (ans += Combination(n, d + 1) * fact[d] % MOD * fact[n - d - 1]) %= MOD; } OUT(ans)BR; return 0; }