# include<stdio.h>
int main()
{
   int n;
   long long result =0;
   scanf("%d",&n);
   if(n<0){
       printf("Invalid input");
       return 0;
   }
   for(int i=1;i<=n;i++){
       long long fact=1;
       for(int j=1;j<=i;j++){
           fact = fact * j;
       }
       if(i%2 == 1){
           result = result + fact;
       }
       else{
           result = result-fact;
       }
   }
   printf("%d",result);
}