d=list(map(int,"".join(reversed("1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991"))))
n=int(input())
t=0
for i in range(len(d)):
    t+=d[i]*n
    d[i] = t - int(t/10)*10
    t = int(t/10)
print(str(t) + "." + "".join(reversed(list(map(str,d)))))