## Problem E: Simple division

Integer division between a dividend **n** and a divisor **d**
yields a quotient **q** and a remainder **r**. **q** is the
integer which maximizes **q*****d** such that **q*****d**
<= **n** and **r** = **n** - **q*****d**.
For any set of integers there is an integer **d** such that each of
the given integers when divided by **d** leaves the same remainder.

Each line of input contains a sequence of nonzero integer numbers
separated by a space. The last number on each line is 0 and this
number does not belong to the sequence. There will be at least 2
and no more than 1000 numbers in a sequence; not all numbers occuring in
a sequence are equal. The last
line of input contains a single 0 and this line should not be
processed. For each line of input, output the largest integer which when
divided into each of the input integers leaves the same remainder.

### Sample input

701 1059 1417 2312 0
14 23 17 32 122 0
14 -22 17 -31 -124 0
0

### Output for sample input

179
3
3

**Problem Setter: Piotr Rudnicki
**