When the third ring is removed, it becomes like this: the third ring is 1 group; The first two rings are 1 group; The last four rings are 1 group.

Form 1, 2, 4 groups.

The first week:1;

Week 2: Get 2 and return to1;

The third week: get1again;

Week 4: Get 4 and return to 1 and 2;

Week 5: Get1again;

Week 6: Get 2 and return to1;

Week 7: Get 1.