#include <bits/stdc++.h>
using namespace std;
int n,a[101],ans;bool b[101];
void all(int x){
    if(x==n+1){
        //for(int i=1;i<=n;i++)cout<<a[i]<<" ";
        //cout<<"  "<<ans<<endl;
		if(a[1]==1)ans++;
		return;
    }
	for(int i=1;i<=n;i++){
		if(b[i])continue;
		a[x]=i;b[i]=true;
		all(x+1);
		b[i]=false;a[x]=0;
	}
}
int main(){
	memset(b,false,sizeof(b));
	cin>>n;
	all(1);
	cout<<ans<<endl;
	return 0;
}

一半TLE，一半WA