Задачі
Hippopotamus
Hippopotamus
You think that your roof looks unpretty. So you opt for a new one, consisting of n consecutive long narrow boards. You have two types of boards: wooden ones and iron ones, giving you an amazing total of 2^n possible roofs.
But the safety should not be left aside. Having considered the weight and the cruising speed of a falling hippopotamus, you decide to have at least k iron boards among every m consecutive boards.
How many possibilities do you have?
Вхідні дані
The input file contains three integers, n, m and k, separated by spaces and/or line breaks. 1 ≤ n ≤ 60, 1 ≤ m ≤ 15, 0 ≤ k ≤ m ≤ n.
Вихідні дані
Output the number of possibilities.
Приклад
Вхідні дані #1
10 2 1
Вихідні дані #1
144