Submission #4301507

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Source Code Expand

#include<bits/stdc++.h>
#define N 1000005
#define p 998244353
#define int long long 
using namespace std;

inline void rd(int &x){
	x=0;char ch=0;int w=0;
	while(!isdigit(ch)) ch=getchar(),w|=ch=='-';
	while( isdigit(ch)) x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
	x=w?-x:x;
}

int n,m,ans;
int f[N],inv[N];

inline int POW(int a,int b=p-2,int ans=1){
	for(;b;b>>=1,a=a*a%p)
		if(b&1) ans=ans*a%p;
	return ans;
}

inline int C(int n,int m){
	return f[n]*inv[m]%p*inv[n-m]%p;
}
signed main(){
	cin>>n>>m;if(n<m) swap(n,m);
	for(int i=f[0]=inv[0]=1;i<=n+m;i++)
		f[i]=f[i-1]*i%p,inv[i]=POW(f[i]);
	for(int i=1;i<=m;i++)
		ans=(ans+C(i<<1,i)*C(n-i+m-i,n-i))%p;
	ans=ans*inv[2]%p*POW(C(n+m,n))%p;
	cout<<(ans+n)%p;
}

Submission Info

Judge Result