#P891A. Pride
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ID: 4078
Type: RemoteJudge
2000ms
256MiB
Tried: 0
Accepted: 0
Difficulty: (None)
Uploaded By:
Hydro
Tags> Pride
No submission language available for this problem.
Description
You have an array a with length n, you can perform operations. Each operation is like this: choose two adjacent elements from a, say x and y, and replace one of them with gcd(x, y), where gcd denotes the greatest common divisor.
What is the minimum number of operations you need to make all of the elements equal to 1?
The first line of the input contains one integer n (1 ≤ n ≤ 2000) — the number of elements in the array.
The second line contains n space separated integers a1, a2, ..., an (1 ≤ ai ≤ 109) — the elements of the array.
Print -1, if it is impossible to turn all numbers to 1. Otherwise, print the minimum number of operations needed to make all numbers equal to 1.
Input
The first line of the input contains one integer n (1 ≤ n ≤ 2000) — the number of elements in the array.
The second line contains n space separated integers a1, a2, ..., an (1 ≤ ai ≤ 109) — the elements of the array.
Output
Print -1, if it is impossible to turn all numbers to 1. Otherwise, print the minimum number of operations needed to make all numbers equal to 1.
Samples
5
2 2 3 4 6
5
4
2 4 6 8
-1
3
2 6 9
4
Note
In the first sample you can turn all numbers to 1 using the following 5 moves:
- [2, 2, 3, 4, 6].
- [2, 1, 3, 4, 6]
- [2, 1, 3, 1, 6]
- [2, 1, 1, 1, 6]
- [1, 1, 1, 1, 6]
- [1, 1, 1, 1, 1]
We can prove that in this case it is not possible to make all numbers one using less than 5 moves.