Pallu works as a bartender in the favorite pub of PP's. Every evening he must present gangster Aditi with a new cocktail: vodka and Margarita, brandy and mango juice, tequilla and lime. The bar owner Zade pays generously for each new cocktail, but on one condition ! Pallu must not repeat the cocktail. Else Zade may shoot him. So Pallu wants to know how soon he will have to leave the town. You are to count how many different cocktails Pallu can make having N components. A cocktail is the mixture of two or more components. Unfortunately, Pallu can’t use one component more than once in the same cocktail. Nevertheless 'vodka and Margarita' and 'Margarita and vodka' are two different cocktails.

Input
The first line of input contains an integer N, an amount of components.

Output
An integer number of cocktails possible.

Constraints
1<=N<=21