#include<bits/stdc++.h>
using namespace std;
int n,m=0,k,l;
void asd(int x){
	m++;
	for(int i=1;i<=x/2;i++){
		asd(i);
	}
}
int main(){
	cin>>n;
	for(int i=1;i<=n/2;i++){
		asd(i);
	}
	cout<<m;
}
/**************************************************************
	Problem: 1307
	User: zhengzihao
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2072 kb
****************************************************************/