#include <iostream> #include <cstdio> #include <iomanip> using namespace std; int main(){ int n,a=2,b=1,t=0; double sum; 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(6)<<sum<<endl; return 0; } |
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