#include <bits/stdc++.h>
#include<atcoder/all>
#define double long double
using namespace std;
int size(int number){
    string numstr=to_string(number);
    return numstr.size();
}
constexpr int MOD=998244353;
signed main(void){
    int N;
    cin>>N;
    vector<int>A(N);
    for(int i=0;i<N;++i){
        cin>>A.at(i);
    }
    vector<map<int,int>>dp(N);
    dp.at(0)[A.at(0)]=1;
    for(int i=1;i<N;++i){
        dp.at(i)=dp.at(i-1);
        if(dp.at(i-1).find(A.at(i)-1)!=dp.at(i-1).end()){
            dp.at(i)[A.at(i)]+=dp.at(i-1)[A.at(i)-1]+1;
            dp.at(i)[A.at(i)]%=MOD;
        }else{
            dp.at(i)[A.at(i)]+=1;
            dp.at(i)[A.at(i)]%=MOD;
        }
        if(i>=2){
            dp.at(i-2).clear();
        }
    }
    int ans=0;
    for(auto e:dp.at(N-1)){
        ans+=e.second;
        ans%=MOD;
    }
    cout<<(ans-A.size())%MOD<<endl;

}