import math
a, b, h, m = map(int, input().split())
hrad = h * 30 + m * 0.5
mrad = m * 6
rad = hrad - mrad
if rad < 0:
    rad = -rad
else:
    if rad > 180:
        rad = 360 - rad
    else:
        pass
c = float((a**2 + b**2 - 2 * a * b * math.cos(math.radians(rad))) ** (0.5))
print(c)
