To participate in a prize draw each one gives his/her firstname. 
Each letter of a firstname
has a value which is its rank in the English alphabet. `A` and `a` have rank `1`, `B` and `b` rank `2` and so on. 
The *length* of the firstname is added to the *sum* of these ranks hence a number `som`. 
An array of random weights is linked to the firstnames and each `som` is multiplied by 
its corresponding weight to get what they call a `winning number`.
Example:
```
names: "COLIN,AMANDBA,AMANDAB,CAROL,PauL,JOSEPH"
weights: [1, 4, 4, 5, 2, 1]
PauL -> som = length of firstname + 16 + 1 + 21 + 12 = 4 + 50 -> 54
The *weight* associated with PauL is 2 so PauL's *winning number* is 54 * 2 = 108.
```
Now one can sort the firstnames in decreasing order of the `winning numbers`. When two
people have the same `winning number` sort them *alphabetically* by their firstnames.
### Task:
- parameters: `st` a string of firstnames, `we` an array of weights, `n` a rank 
- return: the firstname of the participant whose rank is `n` 
(ranks are numbered from 1)
### Example:
```
names: "COLIN,AMANDBA,AMANDAB,CAROL,PauL,JOSEPH"
weights: [1, 4, 4, 5, 2, 1]
n: 4
The function should return: "PauL"
```
# Notes:
- The weight array is at least as long as the number of names, it can be longer.
- If `st` is empty return "No participants".
- If n is greater than the number of participants then return "Not enough participants".
- See Examples Test Cases for more examples.
def win_num(name, weight):
    return (len(name) + sum(ord(c)-96 for c in name.lower())) * weight

def rank(st, we, n):
    if not st:      return "No participants"
    elif n>len(we): return "Not enough participants"
    else:           return sorted((-win_num(s,w),s) for s,w in zip(st.split(","), we))[n-1][1]

def win_num(name, weight):
    return (len(name) + sum(ord(c)-96 for c in name.lower())) * weight

def rank(st, we, n):
    if not st:      return "No participants"
    elif n>len(we): return "Not enough participants"
    else:           return sorted((-win_num(s,w),s) for s,w in zip(st.split(","), we))[n-1][1]
