Marked_fghfzyxf(x,g(x))xf(x,h(y))f(h(x),y)f(x,g(x))xf(x,h(y))f(h(x),y)Marked_f(x,h(y))Marked_f(h(x),y)f(x,g(x))xf(x,h(y))f(h(x),y)Marked_f(x,h(y))Marked_f(h(x),y)Marked_f2Marked_f(x,h(y))Marked_f(h(x),y)f(x,g(x))xf(x,h(y))f(h(x),y)