#include <algorithm>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <memory>
#include <queue>
#include <deque>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#include <cassert>
#include <iostream>
#include <stdio.h>
#include <time.h>
 
using namespace std;
 
#define sz size()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(c) (c).begin(), (c).end()
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define clr(a, b) memset((a), (b) ,sizeof(a))
 
#define MOD 1000000007

int main(){
  int n;
  cin>>n;
  int ans = 0;
  rep(i,1,(1<<n)-1){
    int mx = -1;
    int mn = 20;
    rep(j,0,n){
      if((i>>j)&1){
        mx = max(mx,j);
      }
      else{
        mn = min(mn,j);
      }
    }
    if(mn<mx)ans++;
  }
  cout << ans << endl;
  return 0;
}