#include<iostream>
#include<cmath>
using namespace std;
int r,n,k;

double NdivK(int round)
{
    int g=n-r;
    int d=n-1;
    double ulamek=1;
    for(int i=0;i<round;i++)
    {
        ulamek*=g;
        ulamek/=d;
        g--;
        d--;
    }
    return ulamek;
}
int main()
{
    cin>>k>>r;
    n=(1<<k);
    int round=1;
    double sum=0;
    int i=1;
    while(round<n-r)
    {
        sum+=NdivK(round);
        //cout<<round<<" ulamek "<<NdivK(round)<<'\n';
        i++;
        round=(1<<i)-1;

    }
    int a=sum;
    cout.precision((int)log10(a)+6);
    cout<<sum;
}