You are given a range of integers {L,L+1,,R}. An integer X is said to be Good if it can be represented as a sum of two (not necessarily distinct) integers in this range. Find the number of distinct Good integers.

Input Format

Two integers L and R

Constraints

1LR10^6

Output Format

the number of Good integers.

Sample Input 0

2 2 

Sample Output 0

1 

Explanation 0

the only good number is 2 + 2 = 4

Sample Input 1

2 3 

Sample Output 1

3 

Explanation 1

There is three good number

2 + 2 = 4

2 + 3 = 5

3 + 3 = 6

Sample Input 2

1 3 

Sample Output 2

5 

Explanation 2

There is 5 distinct integers

1 + 1 = 2

1 + 2 = 3

1 + 3 = 4 OR 2 + 2 = 4

2 + 3 = 5

3 + 3 = 6