#include<stdio.h>
int?fun(int?n){
????if?(n==1)
????????return?1;
????return?n*fun(n-1);
}
int?main(){
????int?n,i,s=0,t;
????scanf("%d",?&n);
????for?(i=1;?i<=n;?i++)?{
????????t=fun(i);
????????s?+=?i%2==1?t:-t;
????}
????printf("%d\n",?s);
????return?0;
}