import math
a,b,h,m=map(int,input().split())
 
dh=30*h+m/2
dm=6*m
 
if dm==dh:
    rad=0
else:
    rad=abs(dm-dh)
    
if rad>180:
    rad=rad-180
    length=math.sqrt(a**2+b**2-2*a*b*math.cos(math.radians(rad)))
 
elif 0<rad and rad<180:
    length=math.sqrt(a**2+b**2-2*a*b*math.cos(math.radians(rad)))
 
elif rad==180:
    length=a+b
    
else:
    length=abs(a-b)
    
print(length)