#include <bits/stdc++.h>
//#include <atcoder/all>
//using namespace atcoder;
using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvvb = vector<vvb>;
#define all(A) A.begin(),A.end()
#define rep(i, n) for (ll i = 0; i < (ll) (n); i++)
using pqr = priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>>;

template<class T>
bool chmax(T& p, T q) {
    if (p < q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}
template<class T>
bool chmin(T& p, T q) {
    if (p > q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}
ll gcd(ll(a), ll(b)) {
    ll c = a;
    while (a % b != 0) {
        c = a % b;
        a = b;
        b = c;
    }
    return b;
}
ll Eugrid(ll A, ll B, ll& x, ll& y) {
    if (B == 0) {
        x = 1;
        y = 0;
        return A;
    }
    ll C = gcd(A, B);
    ll D = Eugrid(B, A % B, y, x);
    y -= A / B * x;
    return D;
}//Ax+By=gcd(A,B)の解

ll N;
vector<pair<ll,ll>> P;
vector<vector<ll>> DP;
bool dfs(ll L,ll R,ll turn){
    if(L>=R){
        return 0;
    }
    if(DP[L][R]!=-1){
        return DP[L][R];
    }
    bool W=0;
    bool D=1;
    rep(i,N){

        if(L<=P[i].first&&P[i].second<=R){
            ll x=dfs(L,P[i].first-1,0);
            ll y=dfs(P[i].second+1,R,0);
            if((x^y)){
                W=1;
            }
        }
    }
    DP[L][R]=W;
    return W;
}


int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    ll N,K;
    cin>>N>>K;
    if(K==1){
        cout<<pow(2,N-K)-N<<endl;
    }
    else{
        cout<<pow(2,N-K)<<endl;
    }
}