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

/**************************************************************
	Problem: 1518
	User: wtq001
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/