Maximise `Z=x+y`
Subject to `x-yle -1, -x+yle0,x,yge0`.

Explanation

To solve the problem of maximizing \( Z = x + y \) subject to the constraints given, we will follow these steps:

### Step 1: Write down the constraints
The constraints are:
1. \( x - y \leq -1 \)
2. \( -x + y \leq 0 \)
3. \( x \geq 0 \)
4. \( y \geq 0 \)
...