n = int(input())
a = list(map(int,input().split()))
aa = a[::1]
mod = 998244353
for i in range(n):
  aa[i] *= pow(2, n-i-1, mod)
  aa[i] %= mod
cml = aa[::1]
for i in range(n-1)[::-1]:
  cml[i] += cml[i+1]

ans = 0
for i in range(n-1):
  tmp =pow(2, n-i-1,mod)-1
  tmp %= mod
  ans += pow(2,i,mod)*(a[i]*tmp - cml[i+1])
  ans %= mod

print(ans)