View Code of Problem 71

#include <iostream>
#include <cstdio>
#include <iomanip>
using namespace std;
int main(){
    int a=2,b=1,n,t;
    double sum=0.0;
    cin>>n;
    for(int i=0;i<n;i++){
        sum+=a*1.0/b*1.0;
        t=a;
        a=a+b;
        b=t;
    }
    cout<<fixed<<setprecision(2)<<sum<<endl;
    return 0;
}