#include <cstdio>
#include <cstring>
#include <cmath>
#include <cassert>
#include <random>
#include <vector>
#include <algorithm>
#include <array>
#include <functional>
#include <utility>
#include <regex>
#include <tuple>
#include <map>

using namespace std;
template<typename T>
constexpr T gcd(T a,T b){
	return a%b?gcd(b,a%b):b;
}

int main(){
	int n,k,cnt=0;
	-scanf("%d%d",&n,&k);
	printf("%d\n",(1<<(n-k))-n*(k==1));
	return 0;
}