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

    Mod=998244353
    two=[1]*(N+1)
    for i in range(1,N+1):
        two[i]=(2*two[i-1])%Mod

    ans=0
    for i in range(N):
        ans+=(two[N-1-i]-two[i])*A[i]
        ans%=Mod
    return ans%Mod

#==================================================
print(solve())