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Competitions

Sum of odd numbers

Find the sum of odd numbers in the range from а to b.

Input

Two integers a and b, not greater than 109 by absolute value.

Output

Print the sum of odd numbers in the range from а to b.

Time limit 5 second
Memory limit 128 MiB
Input example #1
2 5
Output example #1
8
Input example #13
-1987655734 1999999734
Output example #13
12305904774248000