You are given (n) points ((x_i, y_i)) on a 2D plane, where (n) is even. Select (\tfrac{n}{2}) disjoint pairs ((a_i, b_i)) to maximize the sum of Manhattan distances between points in pairs. In other words, maximize ()\sum_{i=1}^{n/2} |x_{a_i} - x_{b_i}| + |y_{a_i} - y_{b_i}|.() Each test contains multiple test cases. The first line contains the number of test cases (t) ((1 \le t \le 10^4)). The description of the test cases follows. The first line of each test case contains a single even integer (n) ((2 \leq n \leq 2 \cdot 10^5)) — the number of points. The (i)-th of the next (n) lines contains two integers (x_i) and (y_i) ((-10^6 \le x_i, y_i \le 10^6)) — the coordinates of the (i)-th point. It is guaranteed that the sum of (n) over all test cases does not exceed (2 \cdot 10^5). For each test case, output (\tfrac{n}{2}) lines, the (i)-th line containing two integers (a_i) and (b_i) — the indices of points in the (i)-th pair. If there are multiple solutions, print any of them. In the first test case, an optimal solution is to select the pairs ((1, 4)) and ((2, 3)), which achieves a distance sum of (5 + 3 = 8). In the second test case, an optimal solution is to select the pairs ((1, 8)), ((9, 10)), ((5, 7)), ((2, 3)), ((4, 6)), which achieves a distance sum of (4 + 7 + 10 + 5 + 7 = 33).