X=int(input())
Y=list(map(int, input().split()))
mod = 998244353
allA, allB = 0, 0

ans1, ans2 = 0, 0
for i in Y:
    allA += i*(i+1)//2
    allB += i

    ans1 += i*(i+1)*(i+2)//6

    
for i in Y:
    ans2 += (allA-i*(i+1)//2)*i + (allB-i)*i*(i+1)//2

print((ans1+(ans2)//2)%mod)