YES

1 decompositions
 #1 -----------
   1: s(p(x1)) -> x1
   2: p(s(x2)) -> x2

@Knuth and Bendix' criterion
--- R
   1: s(p(x1)) -> x1
   2: p(s(x2)) -> x2

--- S
   1: s(p(x1)) -> x1
   2: p(s(x2)) -> x2