import math
values = raw_input().split(' ')
a = float(values[0])
b = float(values[1])
c = float(values[2])
d = float(values[3])
if (math.fabs(a*b-c*d)<0.001):
    print "Impossible."

j = 0.0
x = a**2 + b**2 #DC**2(1)
y = c**2 + d**2 #DC**2(2)
x1 = - 2 * a * b
y1 = - 2 * c * d
l = math.fabs(x - y)
r = math.fabs(x1 - y1)
if r == 0:
    False
else:
    j = l / r #cos
    res = a**2.0 + b**2.0 - 2.0 * a * b *j #DC**2
    res = math.sqrt(res)*1000 #DC
    print "Distance is %(res)d km." %{"res": res}


Edited by author 29.04.2016 15:30

Edited by author 29.04.2016 16:01