#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

int fact(int z)
{
    int f = 1, i;
    if (z == 0)
    {
        return(f);
    }
    else
    {
        for (i = 1; i <= z; i++)
	{
            f = f * i;
	}
    }
    return(f);
}

long int countArray(int n, int k, int x) {
    // Return the number of ways to fill in the array.
    int r=n-2;
    n=k;
    int ncr = fact(n) / (fact(r) * fact(n - r));
    int val=2*ncr;
    if(k>=1)
    {
        r=r-1;
        val=val-pow(2,r); 
    }
    if(x<=k)
    {
        val=val-pow(2,r)+1;
    }
    return val;
    
}

int main() {
    int n; 
    int k; 
    int x; 
    scanf("%i %i %i", &n, &k, &x);
    long int answer = countArray(n, k, x);
    printf("%ld\n", answer);
    return 0;
}