k = int(input())

E = {k: 0, k + 1: 0, k + 2: 0, k + 3: 0, k + 4: 0, k + 5: 0, k + 6: 0}
def rec(x):
    if x in E:
        return E[x]
    res = 1.0
    for i in range(1, 7):
        res += rec(x + i) / 6
    E[x] = res
    return res

print(rec(0))