big = 1 000 000
s = 0
S = []
unseen = 1
seen(v) = if (v < big, bittest(s, v), setsearch(S, v))
see(v) = if (v < big, s = bitor(s, 2^v), S = setunion(S, [v])); while (seen(unseen), unseen++)

base = 10

other(n) = {
	my (d = digits(n, base)[1]);
	forstep (v = ceil(unseen/d)*d, oo, d,
		if (!seen(v),
			see(v);
			return (v);
		);
	);
}

for (n = 1, 10 000, print (n " " other(n)))

quit