Compute the Length of a Line Segment

Given the coordinates of two endpoints of a line segment, A(X_a, Y_a) and B(X_b, Y_b), compute the length of the line segment AB.

The length is calculated using the formula:

$$d = \sqrt{(X_b - X_a)^2 + (Y_b - Y_a)^2}$$

inputFormat

The input consists of a single line containing four numbers: X_a, Y_a, X_b, Y_b.

outputFormat

Output the length of the line segment, formatted to six decimal places.

sample

0 0 3 4

5.000000