#include<bits/stdc++.h>
using namespace std;
int main()
{
	long long n,sum = 1;
	cin >> n;
	for( int i = 1; i <= n; i+=2)
	{
		sum *= i;
	}
	cout << sum;
 } 
/**************************************************************
	Problem: 1004
	User: yangwanning
	Language: C++
	Result: Wrong Answer
****************************************************************/