import math

rawUsrInput = input()
usrInput = rawUsrInput.split()

a = int(usrInput[0])
b = int(usrInput[1])
x = int(usrInput[2])

print(90 - float(math.degrees(math.acos((b)/(math.sqrt((4*x**2)/(a**2*b**2)+b**2))))))