import math

a, b, h, m = map(int, input().split())

deg_h = 360 / 12
deg_m = 360 / 60

H = h * deg_h + m * deg_m
M = m * deg_m
deg = abs(H - M)

if deg > 180:
    deg = 360 - deg

rad = (deg/180) * math.pi
c = math.sqrt(a**2 + b**2 - 2*a*b*math.cos(rad))
print(c)
