import sys
input = sys.stdin.readline
MOD = 998244353
X = int(input())
Y = list(map(int, input().split()))
S = [0]
base = 0
for y in Y:
    S.append(S[-1]+y)
    base += y*(y+1)//2
    base %= MOD
ans = base
tmp = 0
for i in range(X):
    y = Y[i]
    ans += base*y%MOD
    ans %= MOD
    cnt = S[-1]-S[i+1]
    ans += (y*(y+1)//2)%MOD * cnt % MOD
    ans %= MOD

    tmp = (y*(y+1)*(2*y+1)//6)%MOD
    tmp %= MOD
    ans -= tmp
    ans %= MOD
    base -= (y*(y+1)//2)
    base %= MOD
    #print(ans)
print(ans)