Submission #1193053

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Source Code Expand

#include <cstdio>
#define N 10003
#define IL inline
#define REP(a,b,c) for(a=b;a<=c;a++)
#define PER(a,b,c) for(a=b;a>=c;a--)
using namespace std;
typedef long long lol;
const lol mod=1e9+7;
int n,a,b,c;lol fac[N],inv[N];
IL lol C(int n,int m){return fac[n]*inv[m]%mod*inv[n-m]%mod;}
IL lol qpow(lol a,int b){lol res=1;while(b){if(b&1)res=res*a%mod;a=a*a%mod,b>>=1;}return res;}
IL lol f(int n,int m){
	if(!n)return m==0;
	return C(n+m-1,m)*inv[n]%mod;
}
int main(){
  scanf("%d%d%d%d",&n,&a,&b,&c);fac[0]=1;int x1,x2,x3,x4,S,up=n<<1,ans=0;
	REP(x1,1,up)fac[x1]=fac[x1-1]*x1%mod;inv[up]=qpow(fac[up],mod-2);
  PER(x1,up,1)inv[x1-1]=inv[x1]*x1%mod;
	for(x2=0;x2<=a&&x2<=c;x2++)
		for(x1=a-x2,S=c-x2,x3=0;S>=0;x3++,S-=3)
	ans=(ans+fac[x1+x2+x3+x4]*inv[x1]%mod*inv[x2]%mod*inv[x3]%mod*f(x4,S))%mod;
	printf("%d\n",ans);
  return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:17:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d%d%d",&n,&a,&b,&c);fac[0]=1;int x1,x2,x3,x4,S,up=n<<1,ans=0;
                                ^

Judge Result