#include<stdio.h> 
int jieCheng(int x){
	int i,s=1;
	for(i = 1;i <= x;i++){
		s *= i;
	}
	return s;
}

int jieChengHe(int n){
	int i,c=0;
	for(i = 1;i <= n;i++){
		c+=jieCheng(i);
	}
	return c;	
}

int main(){ 
	int n;
	scanf("%d",&n);
	printf("%d",jieChengHe(n));
	return 0;
} 

/**************************************************************
	Problem: 1019
	User: admin
	Language: C
	Result: Accepted
	Time:10 ms
	Memory:1144 kb
****************************************************************/