View Code of Problem 71

#include <cstdio>
#include <iostream>
using namespace std;
int main(){
	double sum=0;
	double a=2;
	double b=1;
	int n;
	cin>>n;
	for(int i=0;i<n;i++){
		sum+=a/b;
		int temp=a;
		a+=b;
		b=temp;
	}
	printf("%.2f\n",sum);
	return 0;
}