You will get an array of numbers. 
Every preceding number is smaller than the one following it.
Some numbers will be missing, for instance:
```
[-3,-2,1,5] //missing numbers are: -1,0,2,3,4
```
Your task is to return an array of those missing numbers:
```
[-1,0,2,3,4]
```
def find_missing_numbers(arr):
    if len(arr):
        return [i for i in range(arr[0],arr[-1]) if i not in arr]
    else :
        return []
def find_missing_numbers(arr):
    if len(arr):
        return [i for i in range(arr[0],arr[-1]) if i not in arr]
    else :
        return []