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ADA Training September 7

Lunch

prb1289 Vlad wants to take for lunch a couple of fruits. He has a different bananas, b different apples and c different pears. In how many ways can he choose 2 different fruits from available?

Input

In a single line three non-negative integers are given: a, b and c. All integers do not exceed 106.

Output

Print the number of ways to choose 2 different fruits for a lunch.

Time limit 1 seconds
Memory limit 128 MiB
Input example #1
3 4 2
Output example #1
26