axiom
    A(144) S(5) D(0) ppppp;

rules 4
    p= F S(S/(1+tau)) qqqq S(S*(1+tau)) F;
    q= F S(S/(1+tau)) pppp S(S*(1+tau)) F;
end

rules 1
    p= F-F;
    q= F+F;
end