import sys
if sys.platform =='ios':
	import clipboard
	a=clipboard.get()
	a = a.split('\n')
	text = '\n'.join(a)
	with open('input_file.txt','w') as f:
		f.write(text)
	sys.stdin = open('input_file.txt')
	
k = int(input())
dp = [0]*21
for i in range(1,21):
	for j in range(min(7,i)):
		dp[i] += dp[i-j]/6
	dp[i] += 1
	
print(dp[k])