#include<stdio.h>
int main()
{
	int n,i;
	double h,zs,count;
	count=0;
	zs=0;
	scanf("%d",&n);
	for(i=1;i<=n;i++){
		zs=zs+1;
		if(i % 2==1){
			count=count+1;
		}
	}
	h=count/zs;
	printf("%.10f",h);
	return 0;
}