#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<pii,int> ppii;
typedef pair<ll,ll> pll;
typedef tuple<ll,ll,ll> tl;
ll mod=1000000007;
ll gcd(ll a,ll b){
  if(a<b)swap(a,b);
  if(a%b==0)return b;
  return gcd(b,a%b);
}
ll lcm(ll a,ll b){
  ll ret=a*b;
  ll u=gcd(a,b);
  return ret/u;
}
int main(){
  ll n,k;cin>>n>>k;
  if(k>n){
    cout<<0<<endl;
    return 0;
  }
  ll ans=pow(2,n-k);
  cout<<ans<<endl;
}