import sys

sys.setrecursionlimit(10 ** 6)
from random import randrange

def II(): return int(sys.stdin.readline())

def main():
    k = II()
    throw=0
    turn=100000
    for _ in range(turn):
        s=0
        while s!=k:
            s+=randrange(1,7)
            throw+=1
            if s>k:s=0
    print(throw/turn)

main()