You are given a sequence of 4 numbers represented as a string. The sequence follows these conditions:

• 1st number = (2nd number / 2) - 2
• 2nd number = (3rd number / 3) - 3
• 3rd number = (4th number / 4) - 4

One number in the sequence is missing, and the remaining numbers are given in the string format.

Your task is to find the missing number.

The length of the input string can be as large as 10^5.

Input

A string s representing the sequence, where one of the four numbers is missing.

Output

Print the missing number.

Constraints

1 ≤ |s| ≤ 10^5

Example

Suppose the sequence is:

8 20 69 292

Check:

20 / 2 - 2 = 8
69 / 3 - 3 = 20
292 / 4 - 4 = 69

So if the input is:

8 20 ? 292

the missing number is:

69