# File lib/rack/utils/okjson.rb, line 374
  def subst(u1, u2)
    if Usurr1 <= u1 && u1 < Usurr2 && Usurr2 <= u2 && u2 < Usurr3
      return ((u1-Usurr1)<<10) | (u2-Usurr2) + Usurrself
    end
    return Ucharerr
  end