View Code of Problem 71

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