255. Check whether the given 4 points form a square or not.

Check whether the given 4 points form a square or not.
Example:
INPUT
10 10
10 20
20 20
20 10
OUTPUT
yes


import math

def dist(x1, y1, x2, y2):
    return math.sqrt((x2 - x1)**2 + (y2 - y1)**2)

def angle(x1, y1, x2, y2, x3, y3):
    a = dist(x1, y1, x2, y2)
    b = dist(x2, y2, x3, y3)
    c = dist(x3, y3, x1, y1)
    angle = math.degrees(math.acos((a**2 + b**2 - c**2)/(2*a*b)))
    return angle

x1, y1 = map(int, input().split())
x2, y2 = map(int, input().split())
x3, y3 = map(int, input().split())
x4, y4 = map(int, input().split())

if dist(x1, y1, x2, y2) == dist(x3, y3, x4, y4) and dist(x1, y1, x3, y3) == dist(x2, y2, x4, y4) and angle(x1, y1, x2, y2, x4, y4) == 90 and angle(x2, y2, x3, y3, x4, y4) == 90:
    print("yes")
else:
    print("no")