Given an array x of size n > 3 and an integer N, return the indices of three elements in the array that sum up to the given integer N. If there is no such triplet, return -1.
For example, given x = [1 4 2 5 8 10] and N = 17, the function should return [2 4 5] because x(2) + x(4) + x(5) = 4 + 5 + 8 = 17. With the same x but N = 24, the function should return -1 because there is no triplet whose sum equals 24.
Note that the list of three indices is not necessarily unique. For example, given x = [1 2 3 4 5 6] and N = 9, the expected output can be either [1 2 6] or [1 3 5] since x(1) + x(2) + x(6) = 1 + 2 + 6 = 9 and x(1) + x(3) + x(5) = 1 + 3 + 5 = 9. The tests simply verify that the sum of the elements at the found indices is correct.
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Nikolaos Nikolaou Dyuman Joshi Riccardo G. CXD

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