#include<stdio.h> int main() { int n,i; double a,b,t; double sum; while(scanf("%d",&n)!=EOF) { if(n<1) continue; a=2.0; b=1.0; sum=0.0; for(i=0;i<n;i++) { sum+=a/b; t=a; a=a+b; b=t; } printf("%0.2lf ",sum); } return 0; }