#include<bits/stdc++.h>
using namespace std;

#include<atcoder/all>
using namespace atcoder;

#define int long long
const long long inf=1LL<<62;

using mint=atcoder::modint998244353;

template<long long mod,long long MAX_N>
struct factional_prime{
	long long inv_[MAX_N+1];
    long long fac_[MAX_N+1];
    long long fac_inv_[MAX_N+1];

    factional_prime(){
        inv_[0]=0;inv_[1]=fac_[0]=fac_[1]=fac_inv_[0]=fac_inv_[1]=1;
        for(long long i=2;i<=MAX_N;i++){
            inv_[i]=((mod-mod/i)*inv_[mod%i])%mod;
            fac_[i]=(fac_[i-1]*i)%mod;
            fac_inv_[i]=(fac_inv_[i-1]*inv_[i])%mod;
        }
    }
    long long inv(long long n){
        if(n<0)return 0;
        return inv_[n];
    }
    long long fac(long long n){
        if(n<0)return 0;
        return fac_[n];
    }
    long long finv(long long n){
        if(n<0)return 0;
        return fac_inv_[n];
    }
    long long nCr(long long n,long long r){
        if(n<r||n<0||r<0)return 0;
        return ((fac_[n]*fac_inv_[n-r])%mod*fac_inv_[r])%mod;
    }
    long long nPr(long long n,long long r){
        if(n<r||n<0||r<0)return 0;
        return (fac_[n]*fac_inv_[n-r])%mod;
    }
};

factional_prime<998244353,5000000> fp;

signed main(){
	int n;cin>>n;
	vector<int> a(n);for(auto&e:a)cin>>e;
	mint ans=1;
	for(int i=0;i<n;i++){
		ans+=fp.nCr(a[i]+i+1,i+1)-fp.nCr(a[i]+i,i);
	}
	cout<<ans.val()<<endl;
}