Competitions
Комбинаторика. Формула
Lunch
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 data
Three non-negative integers are given: a, b and c. All integers do not exceed 10^6.
Output data
Print the number of ways to choose 2 different fruits for a lunch.
Examples
Input example #1
3 4 2
Output example #1
26