import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static long factorial(int n) {
        long result = 1;
        for (int i = n; i > 0; i--) {
            result *= i;
        }
        return result;
    }
    
    static long countArray(int n, int k, int x) {
        // Return the number of ways to fill in the array.
        return ((factorial(k + n - 3) / ((factorial(k) * (factorial(n - 3))))) - 1);
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int k = in.nextInt();
        int x = in.nextInt();
        long answer = countArray(n, k, x);
        System.out.println(answer);
        in.close();
    }
}