#include<bits/stdc++.h> using namespace std; #define int long long int read(){int x=0,f=1;char c=getchar();while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}while(c>='0'&&c<='9')x=x*10+c-'0',c=getchar();return x*f;} const int MAXN=300010,Mod=998244353; int Pow(int x,int y){int rt=1;while(y){if(y&1)rt=rt*x%Mod;x=x*x%Mod;y>>=1;}return rt;} void add(int &x,int y){x+=y;if(x>=Mod)x-=Mod;} int n,a[MAXN],f[MAXN],jc[MAXN],ny[MAXN]; int C(int x,int y){return (x<y)?0:jc[x]*ny[y]%Mod*ny[x-y]%Mod;} void slv(){ n=read(); for(int i=1;i<=n;i++)a[i]=read(); jc[0]=ny[0]=1; for(int i=1;i<=MAXN-5;i++)jc[i]=jc[i-1]*i%Mod,ny[i]=Pow(jc[i],Mod-2); int ans=1; for(int i=1;i<=n;i++){ ans=ans*C(a[i]+a[i+1]-1,a[i+1])%Mod; } printf("%lld",ans); } signed main(){ // freopen("euler.in","r",stdin);freopen("euler.out","w",stdout); slv(); return 0; }