### A strange lift

Time Limit: 1000 ms Memory Limit: 65536 KiB

#### Problem Description

There is a strange lift.The lift can stop can at every floor as you want, and there is a number Ki(0 <= Ki <= N) on every floor.The lift have just two buttons: up and down.When you at floor i,if you press the button "UP" , you will go up Ki floor,i.e,you will go to the i+Ki th floor,as the same, if you press the button "DOWN" , you will go down Ki floor,i.e,you will go to the i-Ki th floor. Of course, the lift can\'t go up high than N,and can\'t go down lower than 1. For example, there is a buliding with 5 floors, and k1 = 3, k2 = 3,k3 = 1,k4 = 2, k5 = 5.Begining from the 1 st floor,you can press the button "UP", and you\'ll go up to the 4 th floor,and if you press the button "DOWN", the lift can\'t do it, because it can\'t go down to the -2 th floor,as you know ,the -2 th floor isn\'t exist.
Here comes the problem: when you is on floor A,and you want to go to floor B,how many times at least he havt to press the button "UP" or "DOWN"?

#### Input

The input consists of several test cases.,Each test case contains two lines.

The first line contains three integers N ,A,B( 1 <= N,A,B <= 200) which describe above,The second line consist N integers k1,k2,....kn.
A single 0 indicate the end of the input.

#### Output

For each case of the input output a interger, the least times you have to press the button when you on floor A,and you want to go to floor B.If you can\'t reach floor B,printf "-1".

#### Sample Input

5 1 5
3 3 1 2 5
0

#### Sample Output

3