move(z) = {
	my (w=max(abs(real(z)), abs(imag(z))));
	if (imag(z)==-w, z+1,
		real(z)==-w, z-I,
		imag(z)==+w, z-1,
	                 z+I);
}

T = matrix(1+2*W=50, 1+2*W)
out(z) = max(abs(real(z)), abs(imag(z)))>W
get(z) = T[real(z)+W+1,imag(z)+W+1]
set(z,v) = T[real(z)+W+1,imag(z)+W+1]=v

a(n) = my (v=0); while (n, if (n%2==0, n\=2^valuation(n,2), my (x=valuation(n+1,2)); n\=2^x; v=max(v,x))); v

{
	z=0;
	n=0;
	v=0;
	while (!out(z),
		if (!get(z),
			v++;
			d=move(z)-z;
			for (k=0, v-1,
				if (out(zd=z+k*d),
					break,
					set(zd, v)
				);
			);
		);
		print (n++ " " get(z));
		z=move(z);
	);
}

quit