B'The sequence of integers a_1, a_2, ... , a_k is called a good array if a_1 = k - 1 and a_1 > 0 . For example, the sequences [3, -1, 44, 0], [1, -99] are good arrays, and the sequences [3, 7, 8], [2, 5, 4, 1], [0] -- are not. A sequence of integers is called good if it can be divided into a positive number of good arrays. Each good array should be a subsegment of sequence and each element of the sequence should belong to exactly one array. For example, the sequences [2, -3, 0, 1, 4] , [1, 2, 3, -3, -9, 4] are good, and the sequences [2, -3, 0, 1] , [1, 2, 3, -3 -9, 4, 1] -- are not. For a given sequence of numbers, count the number of its subsequences that are good sequences, and print the number of such subsequences modulo 998244353. The first line contains the number n~(1 <= n <= 10^3) -- the length of the initial sequence. The following line contains n integers a_1, a_2, ... , a_n~(-10^9 <= a_i <= 10^9) -- the sequence itself. In the single line output one integer -- the number of subsequences of the original sequence that are good sequences, taken modulo 998244353. In the first test case, two good subsequences -- [a_1, a_2, a_3] and [a_2, a_3] . In the second test case, seven good subsequences -- [a_1, a_2, a_3, a_4], [a_1, a_2], [a_1, a_3], [a_1, a_4], [a_2, a_3], [a_2, a_4] and [a_3, a_4] . '...