so=[2,3,5,7,11,13]
go=[4,6,8,9,10,12]
n=int(input())
k=1/36
kak=0
for i in range(6):
    for j in range(6):
        if n==so[i]*go[j]:
            kak=kak+k
        j=j+1    
    i=i+1
print("{0:0.19f}".format(kak))