**Problem statement** Sum of Pairs

From my understanding, a good array is an array of the form:

p1[0] + p2[0] = p11 + p21 = p1[2] + p2[2]

But according to the one of the solution that I copied from the submission board, the answer for the following array:

**47, 44, 62, 57, 37**

is **4**. Is it correct? I just can’t see any subset of length 4 which satisfies the above condition. So could anyone shed me a light on this problem? Thanks.