resource main()
  op swap(var int x)
  process p1  {
    int  y
    call swap(y)
  }
  process p2  {
    int  z
    call swap(z)
  }
  process q  {
    int  x1,x2
    in swap(x1) -> in swap(x2) -> x1 :=: x2 ni ni
  }
end
