import java.math.BigInteger;
import java.util.Scanner;

public class Main {

    public static int MAX = 41;
    public static long c[][] = new long[MAX][];

    public static void main(String[] args) {
        for (int i = 0; i < MAX; ++i) {
            c[i] = new long[i + 1];
            for (int j = 0; j <= i; ++j) {
                if ((j == 0) || (j == i)) {
                    c[i][j] = 1;
                } else {
                    c[i][j] = c[i - 1][j] + c[i - 1][j - 1];
                }
            }
        }
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int a = sc.nextInt();
        int b = sc.nextInt();
        BigInteger res = BigInteger.valueOf(c[n + a][a]);
        res = res.multiply(BigInteger.valueOf(c[n + b][b]));
        System.out.println(res);
    }

}