201230: [AtCoder]ARC123 A - Arithmetic Sequence

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.

Constraints

• $1\leq A_1, A_2, A_3\leq 10^{15}$

Input

Input is given from Standard Input in the following format:

$A_1$ $A_2$ $A_3$

Output

Print the answer.

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