#include<stdio.h> #include<cstdlib> #include<cmath> #include<iostream> #include<algorithm> #include<string> using namespace std; typedef long long ll; int main(){ int n; scanf("%d",&n); if(n==1) printf("%.6f\n",2.0/1); double m=2.0,a=1.0,sum=2.0; for(int i=1;i<n;i++){ double t=m,t1=a; m=t+t1; a=t; sum=sum+m/a; } printf("%.6f\n",sum); /*double m=3.0,n=2.0; printf("%.6f",m/n);*/ return 0; } |
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