F. Permutation
data structures; divide and conquer; hashing
You are given a permutation of numbers from 1 to n. Determine whether there's a pair of integers a, b (1 ≤ a, b ≤ n; a ≠ b) such that the element (note, that it is usual division, not integer one) is between a and b in this permutation.
First line consists of a single integer n (1 ≤ n ≤ 300000) — the size of permutation.Second line contains n integers — the permutation itself.
Print ""YES"", if such a pair exists, ""NO"" otherwise (in both cases without quotes, the answer is case insensitive).
In the second example 2 is between 1 and 3. Additionally 4 is between 3 and 5.