# 50115. Depth of Water

## I'm a slow walker, but I never walk backwards.

We have a water tank and a brick. The tank is a cuboid with water in it. The width and length of the tank are $a$ and $b$ respectively. The depth of the water in the tank is $h$. We also have a brick. The width, length of the brick are $c$ and $d$ respectively.

We now place the brick into the water tank. We assume that the brick is heavier than water so it will sink to the bottom of the tank. We also assume that the height of the brick is taller than the tank, and the water will never spill out of the tank.

Write a program to compute the depth of the water after putting the brick into the tank.

sample

## Input Format

The input has five lines for positive integers $a$, $b$, $h$, $c$, and $d$.

## Output Format

The out has only one integer, which is the depth of water after placing the brink into the tank. We assume that the answer is always a positive integer.

## Sample Input

102051510


## Sample Output

20