Process.

1. if size (event) ≥ 3 then//size(∙) calculates the number of members in a set.

2. if s_i, s_i?1 and s_i?2 are same then

3. S←L

4. endif

5. if s_i and s_i?2 are same then

6. S←P

7. endif

8. else

9. S←R

10. endif

11. return(S)