A figure-8 scheme of a storage-ring collider with zero-angle collision and electron and positron beams of equal currents but different energies is considered. In the common straight section, both electrons and positrons move in both directions. Outside the common straight section, electrons and positrons circulate in separated loops (which "reflect" both beams to the common straight section). Therefore, in a multi-bunch mode one can provide collision of four bunches and space charge compensation. This configuration can be considered as the combination of an electron storage ring with electron-electron collisions and a positron storage ring with positron-positron collisions. The new scheme can solve the well-known problem of separating instabilities of compensation in the case of four beams.