#include<bits/stdc++.h>
using namespace std;
int n,s;
int ss(int x){
	if(x==1) return 0;
	if(x==2) return 1;
	return (n-1)*(ss(x-1)+ss(x-2));
}
int main(){
	cin>>n;	
	cout<<ss(n);
return 0;}

/**************************************************************
	Problem: 1694
	User: fzy001
	Language: C++
	Result: Wrong Answer
****************************************************************/