#include<stdio.h>

int main(void){
  int i, j;
  int K;
  int S[6] = {2,3,5,7,11,13};
  int G[6] = {4,6,8,9,10,12};
  int n = 0;
  scanf("%d", &K);
  for(i = 0; i < 6; i++){
    for(j = 0; j < 6; j++){
      if(S[i] * G[j] == K) n++;
    }
  }
  printf("%.12lf\n", (double)n / 36);
  return 0;
}