YES
Time: 0.210

Problem:
 Equations:
  
 TRS:
  fAC(fAC(i(x),i(y1)),y2) -> fAC(i(fAC(x,y1)),y2)
  fAC(one(),x) -> x
  phi(one(),x) -> x
  fAC(i(x),x) -> one()
  i(one()) -> one()
  i(i(x)) -> x
  phi(x,phi(y1,y2)) -> phi(fAC(x,y1),y2)
  fAC(i(fAC(x,y1)),y1) -> i(x)
  i(fAC(i(y1),x)) -> fAC(i(x),y1)
  fAC(i(x),i(y1)) -> i(fAC(x,y1))

Proof:
 AC-KBO Processor:
  precedence:
   fAC > phi ~ one ~ i
   weight function:
    [phi](x0, x1) = x0 + 6x1 + 9,
    
    [one] = 8,
    
    [i](x0) = 8x0 + 7,
    
    [fAC](x0, x1) = x0 + x1 + 1
   problem:
    Equations:
     
    TRS:
     
   Qed