Why this unterminated loop error?

rfin := proc(m::integer) 
local c, i, flg := 0;
for i from 0 to m do
	local b := i;
	do 
		c := b mod 3;
		if (c <> 2) then next else flg := 1; 
		end if;
		b := 1/3*b - 1/3*c;
	until b = 0;
	if evalb(flg = 0) then print(i); 
	end if; 
end do;
end proc;

Hello everyone. I've written a procedure that outputs all numbers <= a given user I/P whose ternary representation has no 2.

However, I get an "Error, unterminated loop" message. Can someone please out the mistake(s)?