Calculus class...is awesome! But you are a programmer with no time for mindless repetition. Your teacher spent a whole day covering differentiation of polynomials, and by the time the bell rang, you had already conjured up a program to automate the process.
You realize that a polynomial of degree n
anx^(n) + an-1x^(n-1) + ... + a0
can be represented as an array of coefficients
[an, an-1, ...,  a0]
For example, we would represent
5x^(2) + 2x + 1 as [5,2,1]
3x^(2) + 1 as [3,0,1]
x^(4) as [1,0,0,0,0]
x as [1, 0]
1 as [1]
Your function will take a coefficient array as an argument and return a **new array** representing the coefficients of the derivative.
```python
poly1 = [1, 1] # x + 1
diff(poly1) == [1] # 1
poly2 = [1, 1, 1] # x^2 + x + 1
diff(poly2) == [2, 1] # 2x + 1
diff(diff(poly2)) == [2] # 2
poly3 = [2, 1, 0, 0] # 2x^3 + x^2
diff(poly3) == [6, 2, 0] # 6x^2 + 2x
```
Note: your function will always return a new array which has one less element than the argument (unless the argument is [], in which case [] is returned).
diff=lambda p:[i*f for i,f in enumerate(p[::-1])][:0:-1]
diff=lambda p:[i*f for i,f in enumerate(p[::-1])][:0:-1]