#include <iostream>
#include <vector>
using namespace std;
typedef unsigned long long ll;
ll calc(ll a,ll b){
  ll s=a-b+1,s2=b;
  vector<ll> vc,vd;
  while(1){
    if(a<s) break;
    vc.push_back(a);
    vd.push_back(b);
    a-=1;
    b-=1;
  }
  for(int i=0;i<s2;++i){
    for(int j=0;j<s2;++j){
      if(vc[i]%vd[j]==0){
        vc[i]/=vd[j];
        vd[j]=1;
      }
    }
  }
  ll c=1,d=1;
  for(int i=0;i<s2;++i){
    c*=vc[i];
    d*=vd[i];
  }
  ll e=c/d;
  return e;
}
int main(){
  ll N;cin>>N;
  ll ans=1;
  ll end=0;
  if(N%2==0){
    end=N/2;
  } else {
    end=N/2+1;
  }
  for(ll i=N-1;i>=end;--i){
    ans+=calc(i,N-i);
  }
  cout<<ans<<endl;
  return 0;
}