[13, 8, -3, 11, 10, -15, 9, -12, 7, 8, -7, 11, -12, -16, 16, -7, -2, 11, 8, 8, 7, -13]

There are 3 index: (13,14,16)

In this case as in many others the solution is not unique, makes it past the kata, waiting a test random which had one index.