#include<bits/stdc++.h>
using namespace std;
int n,sum = 0;
cmwl(int s)
{
	for( int i = 1; i <= s / 2; i++)
	{
		sum++;
		f(i)
	}
}
int main(){
	cin >> n;
	cmwl(n)
	cout << sun;
	return 0;
}

/**************************************************************
	Problem: 1307
	User: yangwanning
	Language: C++
	Result: Compile Error
****************************************************************/