import java.util.*;
import java.lang.*;
import java.io.*;
class Main
{
{
int n, m, d;
Scanner in
= new Scanner
(System.
in); n = in.nextInt();
m = in.nextInt();
d = func(m, n);
}
public static int func (int m, int n){
if (m == 0 || m == n) return 1;
else return func(m - 1, n - 1) + func(m, n - 1);
}
}
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