from collections import deque
D = "1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991"
N = int(input())
dq = deque()
appendleft = dq.appendleft
m = 0
for c in D[::-1]:
    n = int(c)*N+m
    appendleft(n%10)
    m = n // 10
appendleft(".")
appendleft(m)
print("".join(map(str, dq)))