F. Non-equal Neighbourstime limit per test3 secondsmemory limit per test512 megabytesinputstandard inputoutputstandard outputYou are given an array of n positive integers a_1, a_2, \ldots, a_n. Your task is to calculate the number of arrays of n positive integers b_1, b_2, \ldots, b_n such that:   1 \le b_i \le a_i for every i (1 \le i \le n), and  b_i \neq b_{i+1} for every i (1 \le i \le n - 1). The number of such arrays can be very large, so print it modulo 998\,244\,353.InputThe first line contains a single integer n (1 \le n \le 2 \cdot 10^5) — the length of the array a.The second line contains n integers a_1, a_2, \ldots, a_n (1 \le a_i \le 10^9).OutputPrint the answer modulo 998\,244\,353 in a single line.ExamplesInput
3
2 2 2
Output
2Input
2
2 3
Output
4Input
3
1 1 1
Output
0NoteIn 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].
3
2 2 2

2
['combinatorics', 'dp', 'math', '*2400']