string - Lua pattern to match similar consecutive digits -

i have string contains digits 2 9, '223488875662264442', guaranteed not contain more 3 adjacent similar digits, example, cannot contain '7777', can contain '27747772'.

i want make pattern matches similar consecutive numbers, example:

    > str = '44788895532244474568884511123331566';     > n in string.gmatch(str,pat) -- pat pattern     >>    print(n);     > end     44     7     888     9     55     ... 

tried patterns '(%d)%1*' no success.

i cannot use regex,i need lua patterns.