import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
sys.setrecursionlimit(10**7)
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

n,m = na()
l = na()
dp = [0]*(n+1)

dp[0] = 1
mod = 998244353

for k in range(1,n+1):
    for j in l:
        if k-j>=0:
            dp[k]+=dp[k-j]*j%mod*(n+1)%mod
            dp[k]%=mod
        if k-j>=0:
            dp[k]-=dp[k-j]*(k-j)%mod
            dp[k]%=mod
    dp[k]*=pow(k,mod-2,mod)
    dp[k]%=mod
print(dp[n]*pow(n+1,mod-2,mod)%mod)