YES

1 decompositions
 #1 -----------
   1: f(x1) -> x1
   2: f(x1) -> f(f(x1))

@Development Closedness
--- R
   1: f(x1) -> x1
   2: f(x1) -> f(f(x1))

--- S
   1: f(x1) -> x1
   2: f(x1) -> f(f(x1))