Turn each character in a string s into its ASCII character code and join them together to create a number.
For example, for string "abc", the number is 979899. We will call this number "num1".
"abc" ➞ "a" = 97, "b" = 98, "c" = 99 ➞ 979899
Then replace any incidence of the number 7 with the number 1, and call this number "num2":
num1 = 979899
num2 = 919899
Return the difference between the sum of the digits in num1 and num2:
(9 + 7 + 9 + 8 + 9 + 9)
- (9 + 1 + 9 + 8 + 9 + 9)
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➞ 6
calc("ABCDabcd") ➞ 12
calc("cdefgh") ➞ 0
calc("ifkhchlhfde") ➞ 6
Lowercase and uppercase characters have different ASCII character codes.