#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <algorithm>
using namespace std;
char in[100], out[100];
int n,s,e;
int f(int a, int b, int c){
	if(a>s-1 or b > e-1) return 0;
	if(c==n) return 1;
	return f(a+1,b+1,c+1) +f(a+1,0,c+1)+f(0,b+1,c+1);
}

int main(){
	scanf("%d %d %d",&n, &s, &e);
	printf("%d",f(0,0,1));
}