#b503. Another Counting 67

Another Counting 67

Note:子任務2「有l=rl=r」是「皆為l=rl=r」,與子任務3「有l=0,r=n1l=0, r=n−1」是「皆為l=0,r=n1l=0, r=n−1

題目 by chrislaiisme