import math r,k=map(int,input().split()) S=r*r*math.pi eps=1e-9 def calc(y): if y<-r+eps: return 0 if y>r-eps: return S if abs(y)0: rad=math.asin(y/r) res=r*r*rad+y*math.cos(rad)*r return S/2+res else: y=abs(y) rad=math.asin(y/r) res=r*r*rad+y*math.cos(rad)*r return S/2-res res=[] for i in range(1,k+1): s=S/(k+1)*i ng,ok=-r,r for _ in range(100): mid=(ng+ok)/2 if calc(mid)>=s: ok=mid else: ng=mid print('{:.20f}'.format(ok))