#include<stdio.h>
void main(void)
{ 
	int i,j,n;
	long sum,term;
	printf("input n: ");
	scanf("%d",&n);
	for(sum=0,i=1;i<=n;++i)
	{ 
		term=1;
		j=1;
		do
		{ 
			term*=i;
		}while(++j<=i);
		sum+=term;
	}
	printf("sum=%ld\n",sum);
}