(VAR x x1 x2 x3 x4 y z )
(RULES 
        f1 -> g1
        f1 -> g2
        f2 -> g1
        f2 -> g2
        g1 -> h1
        g1 -> h2
        g2 -> h1
        g2 -> h2
        e1(h1,h2,x,y,z) -> e2(x,x,y,z,z)
        e2(f1,x,y,z,f2) -> e3(x,y,x,y,y,z,y,z,x,y,z)
        e3(x1,x1,x2,x2,x3,x3,x4,x4,x,y,z) -> e4(x1,x1,x2,x2,x3,x3,x4,x4,x,y,z)
        e4(g1,x1,g2,x1,g1,x1,g2,x1,x,y,z) -> e1(x1,x1,x,y,z)
        
)