HDU 5879 Cure .

题目地址：http://acm.hdu.edu.cn/showproblem.php?pid=5879

#include<iostream>#include<cstdio>#include<cmath>#include<string>using namespace std;typedef long long LL;double f[1000000+5];string s;int Read(){int n=0;if(s.size()>=7) return 1000000;for(int i=0;i<s.size();i++)n=n*10+s[i]-'0';return n;}int main(){int n;for(int i=1;i<=1000000;i++) f[i]=1.0/((LL)i*i)+f[i-1];while(cin>>s){n=Read();printf("%.5lf\n",f[n]);}return 0;}