//g++ 2.cpp -std=c++14 -O2 -I .
#include <bits/stdc++.h>
using namespace std;

#include <atcoder/all>
using namespace atcoder;

using ll = long long;
using ld = long double;

using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vld = vector<ld>;
using vvld = vector<vld>;
using vst = vector<string>;
using vvst = vector<vst>;

#define fi first
#define se second
#define pb push_back
#define pq_big(T) priority_queue<T,vector<T>,less<T>>
#define pq_small(T) priority_queue<T,vector<T>,greater<T>>
#define all(a) a.begin(),a.end()
#define rep(i,start,end) for(ll i=start;i<(ll)(end);i++)
#define per(i,start,end) for(ll i=start;i>=(ll)(end);i--)
#define uniq(a) sort(all(a));a.erase(unique(all(a)),a.end())

constexpr ll mod = 998244353;

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int n;
  ll s;
  cin>>n>>s;

  ll inv_s=pow_mod(s,mod-2,mod);

  vll p(n);
  rep(i,0,n){
    cin>>p[i];
    p[i]*=inv_s;
    p[i]%=mod;
  }

  vll q={1},r={0};
  rep(i,0,n){
    vll a={1,p[i]};
    vll b={0,(p[i]*p[i])%mod};

    vll x=convolution(q,a);
    vll y=convolution(q,b);
    vll z=convolution(r,a);

    rep(i,0,z.size()){
      if(i<y.size()){
        y[i]+=z[i];
        y[i]%=mod;
      }
      else{
        y.emplace_back(z[i]);
      }
    }

    q=x,r=y;
  }

  ll ans=0;
  ll fractal=2;
  rep(i,1,r.size()){
    ans+=r[i]*fractal;
    ans%=mod;
    fractal*=i+2;
    fractal%=mod;
  }

  cout<<ans<<endl;
}