#include<stdio.h>
int main(){
	int n,i;
	int s=0, p=1;
	printf("S(n)=1+1.2+1.2.3+...+1.2.3...n\n");
	do{
		printf("n = ");
		scanf("%d",&n);
	} while ( n<=0);
	for (i=1; i<=n; i++){
		p*=i;
		s+=p;
	}
	printf("S(%d) = %d",n,s);

	return 0;
}