MOD = 998244353

def inverse(n, d):
    return n * pow(d, -1, MOD) % MOD

half = inverse(1, 2)
def rangeSUM(l, r, c):
    return (l+r)*c%MOD*half%MOD
half2 = inverse(1, 3)
def S(n):
    return n*(n+1)%MOD*(n+2)%MOD*half2%MOD

X = int(input())
Y = list(map(int, input().split()))

sumY = sum(Y)+1
ans = 0
for y in Y:
    if y == 1:
        ans += sumY-1
        ans %= MOD
        continue
    SUM = rangeSUM(sumY-1, (sumY-1)*y, y)
    SUM -= S(y-1)
    SUM %= MOD
    ans += SUM
    ans %= MOD

print(ans)