//
//  main.cpp
//  排列杆子
//
//  Created by Qing Liu on 16/3/29.
//  Copyright © 2016年 Qing Liu. All rights reserved.
//

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>
using namespace std;
long long f[26][26][26];
int main(int argc, const char * argv[]) {
    freopen("pole.in", "r", stdin);
    freopen("pole.out", "w", stdout);
    int n,l,r;
    cin>>n>>l>>r;
    f[1][1][n]=1;
    for (int i=n-1; i>=0; i--) {
        for (int ll=1; ll<=l; ll++) {
            for (int rr=1; rr<=r; rr++) {
                f[ll][rr][i]=f[ll][rr-1][i+1]+f[ll-1][rr][i+1];
                f[ll][rr][i]+=(n-i-1)*f[ll][rr][i+1];
            }
        }
    }
    cout<<f[l][r][1];
    return 0;
}