#include <stdio.h>

int main(void)
{
	int k,i,j,a[6]={2,3,5,7,11,13},b[6]={4,6,8,9,10,12},s=0;
	scanf("%d",&k);
	for(i=0;i<6;i++)for(j=0;j<6;j++)if(k==a[i]*b[j])s++;
	printf("%.13f",s/36.);
	return 0;
}