>>45
x1 -> G(F(F(G(x2,x2))),F(G(x2,x2)))
x2 -> x2
x3 -> F(F(G(x2,x2)))
x4 -> F(G(x2,x2))
x5 -> F(F(G(x2,x2)))
x6 -> F(G(x2,x2))
x7 -> G(F(F(G(x2,x2))),F(G(x2,x2)))