观察表达式的规律，计算前n项的和

观察下列表达式的规律，计算前n项的和2/1 + 3/2 +5/3 +8/5 +13/8+ 21/13思路：不能由斐波那契额数推分母分子分别为前两项分母分子的和，因为n == 100时，斐波那契数会很大，超出范围，所以找规律：F(n) = 1/F(n-1)+1;#include <stdio.h>#include <iostream>#include <string.h>#include <algorithm>#include <math.h>#include <ctype.h>#include <time.h>#include <queue>#include <iterator>using namespace std;int n;double a = 2;int main(){while (cin >> n){double sum = 2;double b = a;for (int i = 2; i <= n; i++){sum += 1 / b + 1;b = 1 / b + 1;}cout << sum << endl;}return 0;}