# -*- coding: utf-8 -*-
import math
n=int(input())
if n == 1: print(1)
elif n == 6: print(3)
else:
    R= 1/(math.sin(math.pi/n))
    if (R-1)>1 :
        R=1/(math.sin(math.pi/(n-1)))
    print (R+1)