#include <stdio.h>
int main() {
int n,i;
__int64 a[21];
a[1] = 0;
a[2] = 1;
for(i = 3;i <= 20;i ++) {
a[i] = (a[i-1] + a[i-2]) * (i-1);
}
while(scanf("%d",&n) != EOF) {
printf("%I64d\n",a[n]);
}
return 0;
}