# coding: utf-8
# Your code here!
import math

n,a,b=list(map(int,input().split()))


d = math.sqrt(((n-1)*(b-a)/2.0)**2 + ((b+a)/2.0)**2)
R=a*b/(d + (b-a)/2.0)
r=a*b/(d - (b-a)/2.0)

ans = (r - R)

print(ans)