Twice Number

Time Limit: 1 sec

 

The Problem

If X is added to twice a number, the sum will be S. What is the number?

 

Example:

if X = 6 and S = 14 then

The number is 4.

 

The Input

The input file contains two integer numbers X (X<=300) and S (S<=500).

 

The Output

Output will show the one integer numbers in a separate line.

 

Sample Input

6 14

 

Sample Output

4

 

 

 

 

Problem Setter: Shahin ShamS