karatsuba := proc (a, b) 
	local n, u, v, w, x, p, l, m; 
	n := max(length(a), length(b)); 
	if a = 0 or b = 0 then return 0 end if; 
	if n = 1 then return a*b end if; 
	if `mod`(n, 2) = 1 then 
		n := 2^floor(log[2](n)+1) ## Bestimmt die kleinste 2er Potenz groesser als n
	end if; 
	u := round(a/10^((1/2)*n)); 
	v := a-u*10^((1/2)*n); 
	w := round(b/10^((1/2)*n)); 
	x := b-w*10^((1/2)*n); 
	p := karatsuba(u, w); 
	l := karatsuba(v, x); 
	m := karatsuba(u-v, x-w); 
	return p*10^n+(p+l+m)*10^((1/2)*n)+l 
end proc