import sys
N=int(input())
if N==0:
	print("0")
	sys.exit()
a=1
b=3
for i in range(1,N):
	a=10 * a + b + ((3*b) //7 )
	b= (3*b) % 7

answer= "0." + "0" * N
a=str(a)
answer=''.join([a[i-(N+2-len(a))] if i>=N+2-len(a) else answer[i] for i in range(N+2)])
print(answer)