hdoj 2156

#include<iostream>#include<stdio.h>using namespace std;int main(){int n;//freopen("in.txt","r",stdin);while(scanf("%d",&n)){if(n==0)return 0;double sum=0;//首先不计算对角线上的int i=1;for(i=2;i<=n;i++){double a=(double)n;double b=(double)i;sum+=(double)((a+1-b)/b);}sum=2*sum;sum+=(double)n;printf("%0.2lf\n",sum);}return 0;}