F - Triples

There is given set of pairwise different points. No three of them have the same Y coordinate (although they may be collinear). Match the points into triples, so that they form triangles (triangles may have area equal to 0), which do not intersect with each other.
Two triangles intersect if any segment of one triangle has at least one point in common with any segment of the other triangle.

Input

Input consists of several sets. Number of sets is given in the first line of input.
Each set starts with N (2<=N<=500), which is followed by descriptions of 3*N points. Point with number i (1<=i<=3*N) is described by pair of integers X_i, Y_i (0 <= X_i, Y_i <= 10000).

Output

For each set output N lines, each one containing 3 integers - numbers of points which are matched into a triple. If there is more than one possibility, output any of them. If there is no possibility, output only one line with word "Impossible" instead N lines with numbers.

Sample Input

2
2
1 2
3 1
3 3
4 1
4 3
6 2
2
1 1
7 1
3 2
5 2
4 3
4 4

Possible Sample Output

1 2 3
4 5 6
1 2 6
3 4 5