YES

   1: +(x1,0()) -> x1
   2: +(x1,s(x2)) -> s(+(x1,x2))
   3: +(x1,+(x2,x3)) -> +(+(x1,x2),x3)
   4: +(+(x1,x2),x3) -> +(x1,+(x2,x3))

@Jouannaud and Kirchner's criterion
--- R
   1: +(x1,0()) -> x1
   2: +(x1,s(x2)) -> s(+(x1,x2))
   3: +(x1,+(x2,x3)) -> +(+(x1,x2),x3)
   4: +(+(x1,x2),x3) -> +(x1,+(x2,x3))

--- S
   1: +(x1,0()) -> x1
   2: +(x1,s(x2)) -> s(+(x1,x2))
   3: +(x1,+(x2,x3)) -> +(+(x1,x2),x3)
   4: +(+(x1,x2),x3) -> +(x1,+(x2,x3))