B'You are given an array of integers a_1, a_2, ldots, a_n . You can do the following operation any number of times (possibly zero): What is the minimum number of operations needed to turn a into an arithmetic progression? The array a is an arithmetic progression if a_{i+1}-a_i=a_i-a_{i-1} for any 2 <= q i <= q n-1 . The first line contains a single integer n ( 1 <= n <= 10^5 ). The second line contains n integers a_1, a_2, ldots, a_n ( 1 <= q a_i <= q 10^5 ). Print a single integer: the minimum number of operations needed to turn a into an arithmetic progression. In the first test, you can get the array a = [11, 10, 9, 8, 7, 6, 5, 4, 3] by performing 6 operations: a is an arithmetic progression: in fact, a_{i+1}-a_i=a_i-a_{i-1}=-1 for any 2 <= q i <= q n-1 . There is no sequence of less than 6 operations that makes a an arithmetic progression. In the second test, you can get the array a = [-1, 2, 5, 8, 11, 14, 17, 20, 23, 26, 29, 32, 35, 38] by performing 10 operations. In the third test, you can get the array a = [100000, 80000, 60000, 40000, 20000, 0, -20000, -40000, -60000, -80000] by performing 7 operations. '...