YES(?,O(n^1))

Problem:
 .(1(),x) -> x
 .(x,1()) -> x
 .(i(x),x) -> 1()
 .(x,i(x)) -> 1()
 i(1()) -> 1()
 i(i(x)) -> x
 .(i(y),.(y,z)) -> z
 .(y,.(i(y),z)) -> z
 .(.(x,y),z) -> .(x,.(y,z))
 i(.(x,y)) -> .(i(y),i(x))

Proof:
 Bounds Processor:
  bound: 1
  enrichment: match
  automaton:
   final states: {4,3,2}
   transitions:
    11() -> 4*,2,1,3
    .0(4,4) -> 2*
    .0(1,4) -> 2*
    .0(4,1) -> 2*
    .0(1,1) -> 2*
    i0(4) -> 3*
    i0(1) -> 3*
    1 -> 2*
    4 -> 2*
  problem:
   
  Qed