32: Sum of score sequences, 32: fractional Sequences

32: Sum of score sequences, 32: fractional Sequences
32: Calculate the fractional sequence and

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Total time limit:

1000 ms

 

Memory limit:

65536kB

Description

There is a fractional sequence q1/p1, q2/p2, q3/p3, q4/p4, q5/p5 ,...., qi + 1 = qi + pi, pi + 1 = qi, p1 = 1, q1 = 2. For example, the first six items of the sequence are 2/1, 3/2, 5/3, 8/5, 13/8, 21/13, respectively. Calculate the sum of the First n items of the fractional sequence.

Input

The input contains a row containing a positive integer n (n <= 30 ).

Output

The output contains a row containing a floating point number, indicating the sum of the First n items in the fractional sequence, which is precise to the fourth digit after the decimal point.

Sample Input

2

Sample output

3.5000

Source

1685

#include<iostream>#include<cstdio>#include<cstring>using namespace std;int ans[10001];double tot=0;int main(){    int n;    cin>>n;    double q=2;    double p=1;    for(int i=1;i<=n;i++)    {        tot=tot+(q/p);        double a=q;        q=a+p;        p=a;    }    printf("%.4lf",tot);    return 0;}