#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

#define rd() ({long _v=0,_c;while(_c=*rp++-48,_c>=0)_v=_v*10+_c;_v;})
#define wt(v) {ulong _z=v;do*--wp=_z%10+48;while(_z/=10);}
#define rep(v,e) for(long v=0;v<e;++v)
#define MD 998244353

typedef unsigned long ulong;

ulong modpow(ulong a, ulong b){
	ulong r=1;
	while(b){
		if(b&1){
			r=r*a%MD;
		}
		b>>=1;
		a=a*a%MD;
	}
	return r;
}


int main(){
	char*mmap();
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	long n=rd();
	ulong z=0;
	ulong u=1;
	ulong v=modpow(2,n);
	rep(i,n){
		ulong a=rd();
		v*=(MD+1)/2;
		v%=MD;
		z=(z+a*(v-u+MD))%MD;
		u*=2;
		u-=u<MD?0:MD;
	}
	char wbuf[64],*wp=wbuf+sizeof wbuf;
	wt(z);
	write(1,wp,wbuf+sizeof wbuf-wp);
	_exit(0);
}