x1 = float(input('input x1: '))
x2 = float(input('input x2: '))
y1 = float(input('input y1: '))
y2 = float(input('input y2: '))
#d3 = (x2-x1)**2
#d4 = (y2-y1)**2
#d5 =d3 + d4
#d6 = d5**0.5
d = (((x2-x1)**2)+((y2-y1)**2))**.5
#print(d6)
print(d)
#work done