Problem Statement

Given is a sequence of three integers A = (A_1, A_2, A_3). On this sequence, you can do the following operation any number of times:

• choose $i\in$ {1,2,3} and add 1 to A_i.

Find the minimum number of operations needed to make A arithmetic. Here, the sequence A = (A_1, A_2, A_3) is arithmetic when A_2 - A_1 = A_3 - A_2 holds.

Input

Input is given from Standard Input in the following format:
A_1 A_2 A_3

Output

Print the answer.

Constraints

• $1\leq A_1, A_2, A_3\leq 10^{15}$

Sample Input 1

4 8 10

Sample Output 1

2

One operation with i = 1 and then one operation with i = 3 yield an arithmetic sequence (5, 8, 11).

Sample Input 2

10 3 4

Sample Output 2

4

Four operations with i = 2 yield an arithmetic sequence (10, 7, 4).

Sample Input 3

1 2 3

Sample Output 3

0

The sequence A is already arithmetic from the beginning, so we need zero operations.

Sample Input 4

1000000000000000 1 1000000000000000

Sample Output 4

999999999999999

见题面 Input 部分

见题面 Output 部分