#include <stdio.h>

int main( ){
	int k;
	int s[6] = { 2, 3, 5, 7, 11, 13 };
	int g[6] = { 4, 6, 8, 9, 10, 12 };
	int count = 0;
	double ans = 0;
	scanf("%d", &k);

	for(int i = 0; i < 6; i++) {
		for(int j = 0; j < 6; j++) {
			if(s[i] * g[j] == k) {
				count++;
			}
		}
	}

	ans = (double)count / 36.0;

	printf("%.14lf\n", ans);
	
	return 0;
}