#include<bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
int main(){
	int N,K;
	cin>>N>>K;
/*
	if(N==2&&K==1){
	   cout<<0<<endl;
	   return 0;
	}
*/
        long long ans;
        long long count;
        if(K!=1){
           ans=1;
           count=1;
           for(int i=K+1;i<=N;i++){ 
              ans+=count;
              count*=2;
           }
        }else{
           ans=0;
           count=1;
           for(int i=K+1;i<=N;i++){
              ans+=count-1;
              count*=2;
           }
        }
        cout<<ans<<endl;
	return(0);
}