Submission #18983105

---

Source Code Expand

//Let's join Kaede Takagaki Fan Club !!
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
typedef pair<int,P> P1;
typedef pair<P,P> P2;
#define pu push
#define pb push_back
#define mp make_pair
//#define eps 1e-7
#define INF 1000000000
#define fi first
#define sc second
#define rep(i,x) for(int i=0;i<x;i++)
#define repn(i,x) for(int i=1;i<=x;i++)
#define SORT(x) sort(x.begin(),x.end())
#define ERASE(x) x.erase(unique(x.begin(),x.end()),x.end())
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin())
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin())
#define all(x) x.begin(),x.end()
template<class T>
void dmp(T a){
	rep(i,a.size()) cout << a[i] << " ";
	cout << endl;
}
template<class T>
bool chmax(T&a, T b){
	if(a < b){
		a = b;
		return 1;
	}
	return 0;
}
template<class T>
bool chmin(T&a, T b){
	if(a > b){
		a = b;
		return 1;
	}
	return 0;
}
template<class T>
void g(T &a){
	cin >> a;
}
template<class T>
void o(const T &a,bool space=false){
	cout << a << (space?' ':'\n');
}
//ios::sync_with_stdio(false);
const ll mod = 1000000007;//998244353
template<class T>
void add(T&a,T b){
	a+=b;
	if(a >= mod) a-=mod;
}

ll F[10005], R[10005];
ll modpow(ll a, ll n){
	ll ret = 1;
	while(n){
		if(n&1) ret = ret * a % mod;
		a = a * a % mod;
		n >>= 1;
	}
	return ret;
}
void init(){
	F[0] = 1;
	for(int i=1;i<10005;i++) F[i] = F[i-1] * i % mod;
	rep(i, 10005) R[i] = modpow(F[i], mod-2);
}
ll C(int a, int b){
	if(b < 0 || a < b) return 0;
	return F[a] * R[b] % mod * R[a-b] % mod;
}
int n, a, b, c;
ll ans;


int main(){
	cin >> n >> a >> b >> c;
	if(b&1){
		cout << 0 << endl; return 0;
	}
	init();
	for(int ac=0;ac<=min(a, c);ac++){
		for(int ccc=0;ccc*3+ac<=c;ccc++){
			ll add = C(ccc+b/2, ccc) * C(ccc+b/2+a, a) % mod * C(a, ac) % mod;
			if(b > 0){
				add = add * C(c-ccc*3-ac+b/2-1, b/2-1) % mod;
			}
			else{
				if(c != ccc*3 + ac) add = 0;
			}
			ans += add;
		}
	}
	cout << (ans%mod) << '\n';
}

Submission Info

Judge Result