+-------------------------------------------+ | | +----+---+ +--------+ +--------+ | | | | | | | | | R(i-2) | | R(i-1) | | R(i) | | | | | | | | | +----+---+ +----+---+ +---+----+ | | | | | | | | | | | | | | | v+ v- | | | | + +--------+ +--------+ | +-----> | | + | | | + | S(i) | +---+> | S(i+1) | +-----------------+> | | | | +--------+ +--------+