import time
start = time.time()
import random

k = int(input())
cnt = 0
tot = 0
while time.time() - start < 1.8:
    x = 0
    cnt += 1
    while x != k:
        tot += 1
        x += random.randrange(1, 7)
        if x > k:
            x = 0
print(tot / cnt)