Cetiri

Mirko has chosen four integers which form an arithmetic
progression. In other words, when the four numbers are sorted,
then the difference between each pair of **adjacent** elements is **constant**.

As has become usual, Mirko **lost** one
of the numbers and also is not sure whether the remaining three
are in the correct (sorted) order.

Write a program that, given the three remaining numbers, finds the fourth number.

The input contains 3 integers between $-100$ and $100$ on a single line, separated by single spaces.

**Note:** the input data will guarantee
that a solution, although not necessarily unique, will always
exist.

Output any number which could have been the fourth number in the sequence.

Sample Input 1 | Sample Output 1 |
---|---|

4 6 8 |
10 |

Sample Input 2 | Sample Output 2 |
---|---|

10 1 4 |
7 |