#include <stdio.h>

int main(void) {
	double e[128]={0.0f};
	int k,i;
	scanf("%d",&k);
	for(i = 101;i <= 100+k;i++){e[i] = ((e[i-1]+e[i-2]+e[i-3]+e[i-4]+e[i-5]+e[i-6])/6)+1;}
	printf("%.12lf",e[100+k]);
	return 0;
}