YES

1 decompositions
 #1 -----------
   1: +(+(x1,x2),x3) -> +(x1,+(x2,x3))
   2: +(x4,+(x5,x6)) -> +(+(x4,x5),x6)

@Rule Labeling
--- R
   1: +(+(x1,x2),x3) -> +(x1,+(x2,x3))
   2: +(x4,+(x5,x6)) -> +(+(x4,x5),x6)

--- S
   1: +(+(x1,x2),x3) -> +(x1,+(x2,x3))
   2: +(x4,+(x5,x6)) -> +(+(x4,x5),x6)