N = int(input())
A = list(map(int, input().split()))
MOD = 998244353

dp = {}
for a in A:
    if a in dp:
        dp[a] = (dp[a]+1) % MOD
    else:
        dp[a] = 1
    # if a+1 in dp:
    #     dp[a]=(dp[a+1]+dp[a])%MOD
    if a-1 in dp:
        dp[a] = (dp[a-1]+dp[a]) % MOD

ans = -N
for k in dp:
    ans = (ans+dp[k]) % MOD
print(ans)