import math
a=float(raw_input('vvedute pervoe 4uslo: '))
b=float(raw_input('vvedute 2-e 4uslo: '))
c=float(raw_input('vvedute 3-e 4uslo: '))
D = math.sqrt(b) - 4*a*c
if D > 0:
	x1 = (-b + (b**2 - 4*a*c))/2*a
else:
	x1 = "kopneu_net"
print x1
raw_input()