'Takes RUT in pure canonical form, calculates the verifier digit.'

def _algorithm(self, rut):

    suma = 0
    multi = 2
    for r in rut[::(-1)]:
        suma += (int(r) * multi)
        multi += 1
        if (multi == 8):
            multi = 2
    return u'0123456789K0'[(11 - (suma % 11))]
