n = int(input())

d = ''
for i in range(101):
    d += str(i+1)

ans = int(d[:190]) * n
s = str(ans)

if n <= 8:
    x = "0." + s
    print(x)
elif 9 <= n and n <= 81:
    x = s[0] + '.'
    for i in range(1, len(s)):
        x += s[i]
    print(x)
else:
    x = s[0] + s[1] + '.'
    for i in range(2, len(s)):
        x += s[i]
    print(x)