WA点：#20

#include<cstdio>
int n,f[35]={1,1};double ans;
int main(){
	for(int i=2;i<=30;i++)f[i]=f[i-1]+f[i-2];
	scanf("%d",&n);
	for(int i=2;i<=n+1;i++)ans+=f[i]*1.0/f[i-1];
	printf("%.4lf",ans);
	return 0;
}