import math
A, B, H, M = map(int, input().split())
Mkaku = 6 * M
Hkaku = (H * 60 + M) / 2
r1 = Hkaku * math.pi / 180
r2 = Mkaku * math.pi / 180
v1x = A * math.cos(r1)
v1y = A * math.sin(r1)
v2x = B * math.cos(r2)
v2y = B * math.sin(r2)
ans = ((v1x - v2x) ** 2 + (v1y - v2y) ** 2) ** 1/2
print(ans)