#include<stdio.h>

int main(){
    int K;
    int i,j;
    int sosuu[6]={2,3,5,7,11,13};
    int gousei[6]={4,6,8,9,10,12};
    double count=0;
	double per;
    
    scanf("%d",&K);
    
    for(i=0;i<6;i++){
        for(j=0;j<6;j++){
            if(K==(sosuu[i]*gousei[j])){
                count++;
               }
        }
    }
	per=count/36;
    printf("%0.12lf\n",per);
    return 0;
}