YES(?,O(n^1))

Problem:
 op(i(x),op(y,z)) -> op(x,op(i(i(y)),z))
 op(i(x),op(y,op(z,w))) -> op(x,op(z,op(y,w)))
 i(x) -> x

Proof:
 Bounds Processor:
  bound: 0
  enrichment: match
  automaton:
   final states: {3,2}
   transitions:
    op0(1,1) -> 2*
    i0(1) -> 3*
    f40() -> 1*
    1 -> 3*
  problem:
   
  Qed