RT

#include <bits/stdc++.h>
using namespace std;
__int128 cache=1;
inline __int128 read(){
	__int128 x=0,f=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){
		if(ch=='-')
			f=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9'){
		x=(x<<1)+(x<<3)+(ch-'0');
		ch=getchar();
	}
	return x*f;
}
void print(__int128 x){
	if(x<0){
		putchar('-');
		x=-x;
	}
	if(x>9)
		print(x/10);
	putchar(x%10+'0');
}
int main(){
	__int128 n;
	__int128 s=0;
	n=read();
	for(n;n>0;n--)
		for(int i=n;i>0;i--){
			cache=cache*i;
			if(i==1){
				s=s+cache;
				cache=1;
			}
		}
		print(s);
		return 0;
}