NO

1 decompositions
 #0 -----------
   1: +(0(),0()) -> 0()
   2: +(s(0()),y) -> s(+(0(),y))
   3: +(x,s(y)) -> s(+(y,x))
   4: s(s(x)) -> x

unjoinable peak
    +(_y6,x)
*<- +(_y6,s(s(x))) ->*
    s(+(s(x),_y6))