# rootit.py
# Fig. 51.2
# inputs: 2

EPS = 1e-10

def rootit(x,y):
  if x < 0:
    raise ValueError('Square root of negatives impossible')
  while abs(x-y) > EPS:
    x = (x+y)/2
    y = a/x
  return x

a = float(input("a? "))
print(f"{rootit(a,1):.10f}")