//KZNS
#include <fstream>
using namespace std;
//
ifstream fin ("pole.in");
ofstream fout ("pole.out");
//
int n, l, r;
long long f[23][23][23] = {0};
//
int main() {
	fin >> n >> l >> r;
	f[n+1][0][0] = 1;
	f[n][1][1] = 1;
	for (int i = n-1; i >= 1; i--) {
		for (int j = 1; j <= l; j++)
			for (int k = 1; k <= r; k++)
				f[i][j][k] = f[i+1][j][k-1] + f[i+1][j-1][k] +f[i+1][j][k]*(n-i-1);
	}
	fout << f[1][l][r];
	return 0;
}
//UBWH