Cute Chef Gift

Chef wants to give a gift to Chefina to celebrate their anniversary. Of course, he has a sequence $a_1, a_2, \ldots, a_N$ ready for this occasion. Since the half-heart necklace is kind of cliche, he decided to cut his sequence into two pieces and give her a piece instead. Formally, he wants to choose an integer $l$ ($1 \le l \lt N$) and split the sequence into its prefix with length $l$ and its su