#include<bits/stdc++.h>
using namespace std;

#define mid(s,e)        (s+(e-s)/2)
#define YES             cout << "YES" << endl
#define NO              cout << "NO" << endl
#define sin(s)	        getline(cin, s)
#define ll              long long
#define ull             unsigned long long
#define dd              double
#define mx 1000005

long factorial(int n)
{
    if(n==0)
        return 1;
    else
        return(n*factorial(n-1));
}

long ncr(int n,int r)
{
    long value;
    value=factorial(n)/(factorial(r)*factorial(n-r));
    return value;
}

int main()
{
    //freopen("A.txt","r",stdin);
    //freopen("A.txt","w",stdout);
    ios_base::sync_with_stdio(0);
    ll n,k,x;
    cin>>n>>k>>x;
    ll m=n-2;
    cout<<ncr(k,m)<<endl;
    return 0;
}