#include #define ADD(a, b) a = (a + ll(b)) % mod #define MUL(a, b) a = (a * ll(b)) % mod #define MAX(a, b) a = max(a, b) #define MIN(a, b) a = min(a, b) #define rep(i, a, b) for(int i = int(a); i < int(b); i++) #define rer(i, a, b) for(int i = int(a) - 1; i >= int(b); i--) #define all(a) (a).begin(), (a).end() #define sz(v) (int)(v).size() #define pb push_back #define sec second #define fst first #define debug(fmt, ...) Debug(__LINE__, ":", fmt, ##__VA_ARGS__) using namespace std; typedef long long ll; typedef unsigned long long ull; typedef pair pi; typedef pair pl; typedef pair ppi; typedef vector vi; typedef vector vl; typedef vector mat; typedef complex comp; void Debug() {cerr << '\n'; } templatevoid Debug(FIRST arg, REST... rest){ cerr<ostream& operator<<(ostream& out,const vector& v) { out<<"[";if(!v.empty()){rep(i,0,sz(v)-1)out<ostream& operator<<(ostream& out,const pair& v){ out<<"("<= b if(a < b || a < 0 || b < 0) return 0; return fac[a] * fiv[b] % mod * fiv[a - b] % mod; } int N, A, B; void solve() { cin >> N >> A >> B; C_init(N); if(A == B) { cout << N * fac[N] % mod << "\n"; return; } if(A > B) swap(A, B); ll a = A, b = B - A, c = N - B; ll res = 0; ADD(res, a * a % mod * fac[N - 1] % mod); ADD(res, b * b % mod * fac[N - 1] % mod); ADD(res, c * c % mod * fac[N - 1] % mod); rep(i, 1, a + 1) { ADD(res, C(b + a - i, a - i) * C(N - 1, c - 1) % mod * fac[a] % mod * fac[b] % mod * fac[c] % mod); } rep(i, 1, c + 1) { ADD(res, C(b + c - i, c - i) * C(N - 1, a - 1) % mod * fac[a] % mod * fac[b] % mod * fac[c] % mod); } cout << res << "\n"; } uint32_t rd() { uint32_t res; #ifdef __MINGW32__ asm volatile("rdrand %0" :"=a"(res) ::"cc"); #else res = std::random_device()(); #endif return res; } int main() { #ifndef LOCAL ios::sync_with_stdio(false); cin.tie(0); #endif cout << fixed; cout.precision(20); cerr << fixed; cerr.precision(6); rng.seed(rd()); #ifdef LOCAL //freopen("in.txt", "wt", stdout); //for tester if(!freopen("in.txt", "rt", stdin)) return 1; #endif solve(); cerr << "Time: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n"; return 0; }