# root
# Fig 51.1
# inputs: 2 1
# x>y

def root(x,y):
  if x == y:
    return x
  else:
    return root((x+y)/2, 2*x*y/(x+y))

x,y = map(float, input("x y=? ").split())
print(f"{root(x,y):.10f}")