#include <bits/stdc++.h>
using namespace std;
const int mod = 998244353;
int mult(int a, int b) { return (1LL * a * b) % mod; }
int sum(int a, int b) {
  int s = a + b;
  if (s >= mod) s -= mod;
  return s;
}
int sub(int a, int b) {
  int s = a - b;
  if (s < 0) s += mod;
  return s;
}
int n;
const int maxN = 5e5 + 10;
int a[maxN];
int dp[maxN];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  dp[0] = 1;
  vector<pair<int, int>> st;
  int cur = 0;
  for (int i = 1; i <= n; i++) {
    int to_add = 0;
    while (!st.empty() && a[st.back().first] >= a[i]) {
      int was_sum = mult(st.back().second, a[st.back().first] % mod);
      cur = sub(cur, was_sum);
      to_add = sum(to_add, st.back().second);
      st.pop_back();
    }
    int p = dp[i - 1];
    if ((i - 1) % 2 == 1) p = sub(0, p);
    to_add = sum(to_add, p);
    cur = sum(cur, mult(to_add, a[i] % mod));
    st.emplace_back(i, to_add);
    if (i % 2 == 1) {
      dp[i] = cur;
    } else {
      dp[i] = sub(0, cur);
    }
  }
  cout << dp[n];
  return 0;
}

### Prompt

Develop a solution in cpp to the problem described below:

You are given an array of n positive integers a_1, a_2, …, a_n. Your task is to calculate the number of arrays of n positive integers b_1, b_2, …, b_n such that: 

  * 1 ≤ b_i ≤ a_i for every i (1 ≤ i ≤ n), and 
  * b_i ≠ b_{i+1} for every i (1 ≤ i ≤ n - 1). 



The number of such arrays can be very large, so print it modulo 998 244 353.

Input

The first line contains a single integer n (1 ≤ n ≤ 2 ⋅ 10^5) — the length of the array a.

The second line contains n integers a_1, a_2, …, a_n (1 ≤ a_i ≤ 10^9).

Output

Print the answer modulo 998 244 353 in a single line.

Examples

Input


3
2 2 2


Output


2

Input


2
2 3


Output


4

Input


3
1 1 1


Output


0

Note

In the first test case possible arrays are [1, 2, 1] and [2, 1, 2].

In the second test case possible arrays are [1, 2], [1, 3], [2, 1] and [2, 3].

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
const int mod = 998244353;
int mult(int a, int b) { return (1LL * a * b) % mod; }
int sum(int a, int b) {
  int s = a + b;
  if (s >= mod) s -= mod;
  return s;
}
int sub(int a, int b) {
  int s = a - b;
  if (s < 0) s += mod;
  return s;
}
int n;
const int maxN = 5e5 + 10;
int a[maxN];
int dp[maxN];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  dp[0] = 1;
  vector<pair<int, int>> st;
  int cur = 0;
  for (int i = 1; i <= n; i++) {
    int to_add = 0;
    while (!st.empty() && a[st.back().first] >= a[i]) {
      int was_sum = mult(st.back().second, a[st.back().first] % mod);
      cur = sub(cur, was_sum);
      to_add = sum(to_add, st.back().second);
      st.pop_back();
    }
    int p = dp[i - 1];
    if ((i - 1) % 2 == 1) p = sub(0, p);
    to_add = sum(to_add, p);
    cur = sum(cur, mult(to_add, a[i] % mod));
    st.emplace_back(i, to_add);
    if (i % 2 == 1) {
      dp[i] = cur;
    } else {
      dp[i] = sub(0, cur);
    }
  }
  cout << dp[n];
  return 0;
}

```