Problem: Write a program which calculates the distance between two points P1(x1, y1) and P2(x2, y2).



Input

Four real numbers x1, y1, x2 and y2 are given in a line.

Output

Print the distance in real number. The output should not contain an absolute error greater than 10-4.

Example

Input

0 0 1 1


Output

1.41421356

Solution (in PYTHON):

Solution:
x1, y1, x2, y2 = map(float, raw_input().split())
num = (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1)
if num == 0:
    print 0
else:
    xi = num
    for _ in range(100):
        xi = (xi + (num / xi)) / 2.0
    print xi