(VAR X N M X1 X2) (RULES a__and(tt,X) -> mark(X) a__plus(N,0) -> mark(N) a__plus(N,s(M)) -> s(a__plus(mark(N),mark(M))) a__x(N,0) -> 0 a__x(N,s(M)) -> a__plus(a__x(mark(N),mark(M)),mark(N)) mark(and(X1,X2)) -> a__and(mark(X1),X2) mark(plus(X1,X2)) -> a__plus(mark(X1),mark(X2)) mark(x(X1,X2)) -> a__x(mark(X1),mark(X2)) mark(tt) -> tt mark(0) -> 0 mark(s(X)) -> s(mark(X)) a__and(X1,X2) -> and(X1,X2) a__plus(X1,X2) -> plus(X1,X2) a__x(X1,X2) -> x(X1,X2) )