Problems

# Sum of even numbers

Find the sum of even numbers on a segment from a to b inclusively.

#### Input

Two integers а and b (аb), no more than 109 by absolute value.

#### Output

Print the sum of even numbers on a segment from a to b inclusively.

Time limit 1 second
Memory limit 128 MiB
Input example #1
1 5

Output example #1
6