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Presumptuous base conversion

Take an input string representing a number and convert it to decimal (base 10). However, the base of the input is **not** specified. Assume the input is in the smallest base for which its digits are valid.

## Input
- The input consists only of characters from 0123456789ABCDEF where A to F represent the decimal numbers 10 to 15
- The answerer may choose to take lower case input instead
- The input will always contain at least one character (it will never be empty)
- The input will sometimes have one or more leading zeroes

## Output
- If the highest digit in the input is represented by N, then the input is to be treated as being in base N+1
- For this challenge, the letters A to F count as "digits". So if the highest digit in the input is B, which represents 11, then the input is in base 12
- In particular, if the highest digit in the input is 0, then the input is to be treated as being in base 1 (unary), so the output is the number of digits in the input
- Apart from inputs in base 1 (unary), leading zeroes make no difference to the output. Both "11" and "000011" lead to output "3"

## Examples
- If the input is **453** then the highest digit is **5**, so the input is in base 6. The output is 177, calculated as **4**[]()\*6\*6 + **5***6 + **3**
- If the input is **000** then the highest digit is **0** so the input is in base 1 (unary). The output is 3, which is simply the length of the unary input

## Test cases
Test cases are in the form `input : output`

```text
0 : 1
1 : 1
9 : 9
A : 10
E : 14
F : 15
00 : 2
01 : 1
10 : 2
11 : 3
02 : 2
20 : 6
22 : 8
65 : 47
99 : 99
AA : 120
B8 : 140
000 : 3
00F : 15
0D0 : 182
C00 : 2028
123 : 27
ABC : 1845
777 : 511
453 : 177
```