Manhattan distance

The streets in the central part of Manhattan are constructed in a way that resembles a grid. To get from one crossroad you need to go parallel in one direction and then vertical in another. So, if we imagine a virtual X and Y axis, in Manhattan, we always move either parallel to the OX axis or parallel to the OY axis.

This construction of streets has become so popular that people started using it as a distance metric. When it’s only allowed to move in the OX or the OY directions and one needs to get from $(x_1, y_1)$ to $(x_2, y_2)$, they first move parallel to the OX axis to get from $x_1$ to $x_2$ and afterward from $y_1$ to $y_2$. This changes the calculations of distance between points and is called Manhattan distance. The standard Euclidean distance is $d = \sqrt{(x2 - x1)^2 + (y2 - y1)^2}$.

Can you figure out the Manhattan distance between two points?

The input consists of 4 numbers: $x_1$ and $y_1$ coordinates of the first point followed by $x_2$ and $y_2$ coordinates of the second point. The program should output the Manhattan distance between those two points.

Input	Output
3 4 1 0.5	5.5