YES(?,O(n^1))

Problem:
 a(a(a(x1))) -> b(b(x1))
 b(b(b(x1))) -> c(d(x1))
 c(x1) -> a(a(x1))
 d(x1) -> c(x1)

Proof:
 Matrix Interpretation Processor:
  dimension: 1
  interpretation:
   [c](x0) = x0 + 29,
   
   [d](x0) = x0 + 30,
   
   [b](x0) = x0 + 20,
   
   [a](x0) = x0 + 14
  orientation:
   a(a(a(x1))) = x1 + 42 >= x1 + 40 = b(b(x1))
   
   b(b(b(x1))) = x1 + 60 >= x1 + 59 = c(d(x1))
   
   c(x1) = x1 + 29 >= x1 + 28 = a(a(x1))
   
   d(x1) = x1 + 30 >= x1 + 29 = c(x1)
  problem:
   
  Qed