#include <algorithm>
#include <bits/stdc++.h>
#ifdef SHO_LOCAL
#include "debug.h"
#else
#define debug(...)                                                             \
  {}
#endif
using namespace std;

constexpr const long long _mod = 998244353;
struct mint;
static vector<mint> inv_memo;
static vector<mint> fact_memo;
struct mint {
  using ll = long long;
  ll raw_val;
  mint(ll x = 0) { raw_val = (x % _mod + _mod) % _mod; }
  inline mint operator-() const { return mint(-raw_val); }
  inline mint &operator+=(const mint a) {
    if ((raw_val += a.raw_val) >= _mod)
      raw_val -= _mod;
    return *this;
  }
  inline mint &operator-=(const mint a) {
    if ((raw_val += _mod - a.raw_val) >= _mod)
      raw_val -= _mod;
    return *this;
  }
  inline mint &operator*=(const mint a) {
    (raw_val *= a.raw_val) %= _mod;
    return *this;
  }
  inline mint operator+(const mint a) const { return mint(*this) += a; }
  inline mint operator-(const mint a) const { return mint(*this) -= a; }
  inline mint operator*(const mint a) const { return mint(*this) *= a; }
  inline mint pow(ll t) const {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }
  inline mint inv() const {
    if ((int)inv_memo.size() > raw_val) {
      return inv_memo[raw_val];
    }
    return pow(_mod - 2);
  }
  inline mint &operator/=(const mint a) { return *this *= a.inv(); }
  inline mint operator/(const mint a) const { return mint(*this) /= a; }
};
static inline mint factorial(int n) {
  mint res(1);
  for (int i = 2; i <= n; i++) {
    res *= i;
  }
  return res;
}
struct mcombination {
  vector<mint> f, invf;
  mcombination(const int n) : f(n + 1), invf(n + 1) {
    f[0] = 1;
    for (int i = 1; i <= n; ++i)
      f[i] = f[i - 1] * i;
    invf[n] = f[n].inv();
    for (int i = n; i >= 1; --i)
      invf[i - 1] = invf[i] * i;
  }
  inline mint _c(const int n, const int k) const {
    if (k < 0 || k > n)
      return 0;
    return f[n] * invf[k] * invf[n - k];
  }
  inline mint operator()(const int n, const int k) const { return _c(n, k); }
  inline mint h(const int n, const int r) const { return _c(n + r - 1, r); }
};
static inline istream &operator>>(istream &is, mint &a) {
  return is >> a.raw_val;
}
static inline ostream &operator<<(ostream &os, const mint &a) {
  return os << a.raw_val;
}

int main() {
  iostream::sync_with_stdio(0), cin.tie(0), cout.tie(0);

  int n;
  cin >> n;
  vector<int> A(n);
  for (int i = 0; i < n; i++) {
    cin >> A[i];
  }
  mint ans;
  for (int i = 0; i < n; i++) {
    int a = A[i];
    if (i < n - 1)
      ans += (mint(2).pow(n - i - 1) - 1) * a;
    ans -= (mint(2).pow(i) - 1) * a;
  }
  cout << ans << '\n';

  return 0;
}