(VAR i x y )
(RULES 
        topB(i,N1(x),y) -> topA(1,T1(x),y)
        topA(i,x,N2(y)) -> topB(0,x,T2(y))
        topB(i,S1(x),y) -> topA(i,N1(x),y)
        topA(i,x,S2(y)) -> topB(i,x,N2(y))
        topA(i,N1(x),T2(y)) -> topB(i,N1(x),S2(y))
        topA(1,T1(x),T2(y)) -> topB(1,T1(x),S2(y))
        topA(i,N1(x),y) ->= topA(1,T1(x),y)
        topB(i,x,N2(y)) ->= topB(0,x,T2(y))
        topA(i,S1(x),y) ->= topA(i,N1(x),y)
        topB(i,x,S2(y)) ->= topB(i,x,N2(y))
        topB(i,N1(x),T2(y)) ->= topB(i,N1(x),S2(y))
        topB(1,T1(x),T2(y)) ->= topB(1,T1(x),S2(y))
        topA(i,N1(x),y) ->= topA(i,N1(C(x)),y)
        topB(i,x,N2(y)) ->= topB(i,x,N2(C(y)))
        topA(i,T1(x),y) ->= topA(i,T1(x),y)
        topB(i,x,T2(y)) ->= topB(i,x,T2(y))
        topB(i,x,S2(y)) ->= topB(i,x,S2(D(y)))
)