#include<iostream>
#include<cstdio>
using namespace std;


long long int derrangement(long long i)
{
    if(i == 1 || i==0) return 0;
    if(i==2) return 1;

    return (i-1) * (derrangement(i-1) + derrangement(i-2));


}
long long int factorial(long long int n)
{
 if(n==0 || n==1) return 1;
   long long sum = 1;
   for(long long int i = 1; i<=n; i++) sum*=i;

   return sum;

}
long long combination(long long int n, long long int r)
{
    long long int factN = factorial(n);
    long long int factR = factorial(r);
    long long int factNR = factorial(n-r);
    return factN/(factNR*factR);
}
int main()
{


    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w+", stdout);
    long long int a, b;
    while(cin>>a>>b)
    {


        long long res = derrangement(a);
        for(long long i=1;i<=b;i++)
        {
            res+=combination(a,i)*derrangement(a-i);
        }
        if(a==b) res++;
        cout<<res<<endl;
    }



    return 0;
}