from functools import cache
import sys
sys.setrecursionlimit(10 ** 6)


@cache
def f(x: int) -> float:
    if x <= 0: return 0

    res = 0
    for i in range(1, 7):
        res += (f(x - i) + 1) / 6

    return res


K = int(input())
ans = f(K)
print(ans)