#include <bits/stdc++.h>
using namespace std;
const long long MOD = 998244353;
int main(){
  int N, M;
  cin >> N >> M;
  vector<int> l(M);
  for (int i = 0; i < M; i++){
    cin >> l[i];
  }
  vector<long long> INV(N + 2);
  INV[1] = 1;
  for (int i = 2; i <= N + 1; i++){
    INV[i] = MOD - INV[MOD % i] * (MOD / i) % MOD;
  }
  vector<long long> a(N + 1, 0);
  a[0] = 1;
  for (int i = 1; i <= N; i++){
    for (int j = 0; j < M; j++){
      if (l[j] <= i){
        a[i] += (long long) (N + 1) * l[j] % MOD * a[i - l[j]] % MOD;
      }
    }
    for (int j = 0; j < M; j++){
      if (l[j] <= i - 1){
        a[i] += MOD - (i - l[j]) * a[i - l[j]] % MOD;
      }
    }
    a[i] %= MOD;
    a[i] *= INV[i];
    a[i] %= MOD;
  }
  cout << a[N] * INV[N + 1] % MOD << endl;
}