??
#include <stdio.h>
#include <stdlib.h>
int main()美国高防vps
{
??? int n,i;
??? double sum=1.0,t,j=1.0;
??? scanf(“%d”,&n);
??? for(i=1;i<=n;i++)
??? {
??????? t=i*j;
??????? sum+=1.0/t;
??????? j=t;
??? }
??? printf(“%.16f”,sum);
??? return 0;
}