Given number N. Calculate how many combinations with N signs possible combine from 1 and 0. Constraints:
- Should always start with 1
- Avoid two digit 1 in series
Examples:
- for n = 1, possible only 1 combination - '1'
- for n = 3, possible 3 combinations - '10', '11'
- for n = 4, possible 3 combinations - '1000', '1001', '1010'
All the same with problem 1, but you should avoid three digit 1 in series