## https://yukicoder.me/problems/no/2550

MOD = 998244353

def main():
    N = int(input())
    A = list(map(int, input().split()))

    pattern_sum = [0] * (N + 1)
    steps_sum = [0] * (N + 1)
    score_sum = [0] * (N + 1)
    cum_pattern_sum = [0] * (N + 1)
    cum_steps_sum = [0] * (N + 1)
    cum_score_sum = [0] * (N + 1)
    pattern_sum[0] = 1
    cum_pattern_sum[0] = 1

    for i in range(N):
        pattern_sum[i + 1] += cum_pattern_sum[i]
        pattern_sum[i + 1] %= MOD

        steps_sum[i + 1] += cum_steps_sum[i]
        steps_sum[i + 1] %= MOD
        steps_sum[i + 1] += cum_pattern_sum[i]
        steps_sum[i + 1] %= MOD

        score_sum[i + 1] += (steps_sum[i + 1] * A[i]) % MOD
        score_sum[i + 1] %= MOD
        score_sum[i + 1] += cum_score_sum[i]
        score_sum[i + 1] %= MOD

        cum_pattern_sum[i + 1] += (pattern_sum[i + 1] + cum_pattern_sum[i]) % MOD
        cum_pattern_sum[i + 1] %= MOD
        cum_steps_sum[i + 1] += (steps_sum[i + 1] + cum_steps_sum[i]) % MOD
        cum_steps_sum[i + 1] %= MOD
        cum_score_sum[i + 1] += (score_sum[i + 1] + cum_score_sum[i]) % MOD
        cum_score_sum[i + 1] %= MOD

    print(score_sum[-1])

if __name__ == "__main__":
    main()