Given a string, turn each letter into its ASCII character code and join them together to create a number - let's call this number `total1`:
```
'ABC' --> 'A' = 65, 'B' = 66, 'C' = 67 --> 656667
```
Then replace any incidence of the number `7` with the number `1`, and call this number 'total2':
```
total1 = 656667
              ^
total2 = 656661
              ^
```
Then return the difference between the sum of the digits in `total1` and `total2`:
```
  (6 + 5 + 6 + 6 + 6 + 7)
- (6 + 5 + 6 + 6 + 6 + 1)
-------------------------
                       6
```
def calc(x):
    return ''.join(str(ord(ch)) for ch in x).count('7') * 6
def calc(x):
    return ''.join(str(ord(ch)) for ch in x).count('7') * 6