#pragma GCC target("avx2") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") #pragma GCC optimize("Ofast") #include #include using namespace std; #if __has_include() #include using namespace atcoder; #endif using ll = long long; using ld = long double; using ull = long long; #define endl "\n" #define REP3(i, m, n) for (int i = (m); (i) < int(n); ++ (i)) #define rep(i,a,b) for(int i=(int)(a);i<(int)(b);i++) #define ALL(x) begin(x), end(x) #define all(s) (s).begin(),(s).end() //#define rep2(i, m, n) for (int i = (m); i < (n); ++i) //#define rep(i, n) rep2(i, 0, n) #define PB push_back #define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i) #define drep(i, n) drep2(i, n, 0) #define rever(vec) reverse(vec.begin(), vec.end()) #define sor(vec) sort(vec.begin(), vec.end()) #define FOR(i,a,b) for(ll i=a;i<=(ll)(b);i++) #define fi first #define se second #define pb push_back #define P pair //const ll mod = 998244353; const ll mod = 1000000007; const ll inf = 4500000000000000000ll; static const long double pi = 3.141592653589793; templatevoid vcin(vector &n){for(int i=0;i>n[i];} templatevoid vcin(vector &n,vector &m){for(int i=0;i>n[i]>>m[i];} templatevoid vcout(vector &n){for(int i=0;ivoid vcin(vector> &n){for(int i=0;i>n[i][j];}}} templatevoid vcout(vector> &n){for(int i=0;iauto min(const T& a){ return *min_element(all(a)); } templateauto max(const T& a){ return *max_element(all(a)); } templatevoid print(pair a){cout<bool chmax(T &a, const T &b) { if (abool chmin(T &a, const T &b) { if (b void ifmin(T t,T u){if(t>u){cout<<-1< void ifmax(T t,T u){if(t>u){cout<<-1<auto make_vector(T x,int arg,Args ...args){if constexpr(sizeof...(args)==0)return vector(arg,x);else return vector(arg,make_vector(x,args...));} ll modPow(ll a, ll n, ll mod) { if(mod==1) return 0;ll ret = 1; ll p = a % mod; while (n) { if (n & 1) ret = ret * p % mod; p = p * p % mod; n >>= 1; } return ret; } vector divisor(ll x){ vector ans; for(ll i = 1; i * i <= x; i++){ if(x % i == 0) {ans.push_back(i); if(i*i!=x){ ans.push_back(x / ans[i]);}}}sor(ans); return ans; } template struct Sum{ vector data; Sum(const vector& v):data(v.size()+1){ for(ll i=0;i struct Sum2{ vector> data; Sum2(const vector> &v):data(v.size()+1,vector(v[0].size()+1)){ for(int i=0;i=n-1&&n-1>=0){ return COM(n+k-1,n-1); } else{ return 0; } } int main() { cincout(); COMinit(); ll n,m; cin>>n>>m; ll ans=n*COM(2*n,n)*2ll; ans%=mod; // cout<>x>>y>>z; if(x==1){ ans-=COM(y+z,z)*COM(n-1-y+n-z,n-z); } else{ ans-=COM(y+z,z)*COM(n-1-y+n-z,n-z-1); } ans%=mod; ans+=mod; ans%=mod; } cout<