Submission #33626826

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
const long long N=4e5+5,mod=998244353;
long long n;
long long mul[N],inv[N];
long long ksm(long long f,long long x){
	long long tot=1;
	while(x){
		if(x & 1ll) tot=1ll*tot*f%mod;
		f=1ll*f*f%mod;
		x>>=1ll;
	}
	return tot;
}
 
void init(long long lim){
	mul[0]=inv[0]=1;
	for(long long i=1;i<=lim;i++) mul[i]=1ll*mul[i-1]*i%mod;
	inv[lim]=ksm(mul[lim],mod-2);
	for(long long i=lim-1;i>=1;i--) inv[i]=1ll*inv[i+1]*(i+1)%mod;
}
long long C(long long m,long long n){
	if(m<0 || n<0 || m<n) return 0;
	return 1ll*mul[m]*inv[n]%mod*inv[m-n]%mod;
}


long long dp[N];
int main(){
	init(N-5);
	cin>>n;
	cout<<C(2*n,n+1)*ksm(n,mod-2)%mod*mul[n]%mod*ksm(2,n)%mod;
}

Submission Info

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