#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int n,i,j,f,s = 0,x;
    f = 1;
    cin>>n;
    for(i = 1;i <= n;i++){
    	x = 1;
    	for(j = 1;j <= i;j++){
    		x = x * j;
		}
    	s = s + f * x;
    	
    	f = f * -1;
	}
	
	cout<<s<<endl;
}
/**************************************************************
	Problem: 1518
	User: admin
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/