Given an integer `n`, find two integers `a` and `b` such that:
```Pearl
A) a >= 0 and b >= 0
B) a + b = n
C) DigitSum(a) + Digitsum(b) is maximum of all possibilities.  
```
You will return the digitSum(a) + digitsum(b). 
```
For example:
solve(29) = 11. If we take 15 + 14 = 29 and digitSum = 1 + 5 + 1 + 4 = 11. There is no larger outcome.
```
`n` will not exceed `10e10`.
More examples in test cases. 
Good luck!
def solve(param):
    a = int('0' + '9' * (len(str(param)) - 1))
    return sum(int(d) for d in str(a) + str(param - a))
def solve(param):
    a = int('0' + '9' * (len(str(param)) - 1))
    return sum(int(d) for d in str(a) + str(param - a))