Black and White Tree

1000ms

262144K

Description:

The board has got a painted tree graph, consisting of n nodes. Let us remind you that a non-directed graph is called a tree if it is connected and doesn't contain any cycles.

Each node of the graph is painted black or white in such a manner that there aren't two nodes of the same color, connected by an edge. Each edge contains its value written on it as a non-negative integer.

A bad boy Vasya came up to the board and wrote number s_v near each node v — the sum of values of all edges that are incident to this node. Then Vasya removed the edges and their values from the board.

Your task is to restore the original tree by the node colors and numbers s_v.

Input:

The first line of the input contains a single integer n (2 ≤ n ≤ 10⁵) — the number of nodes in the tree. Next n lines contain pairs of space-separated integers c_i, s_i (0 ≤ c_i ≤ 1, 0 ≤ s_i ≤ 10⁹), where c_i stands for the color of the i-th vertex (0 is for white, 1 is for black), and s_i represents the sum of values of the edges that are incident to the i-th vertex of the tree that is painted on the board.

Output:

Print the description of n - 1 edges of the tree graph. Each description is a group of three integers v_i, u_i, w_i (1 ≤ v_i, u_i ≤ n, v_i ≠ u_i, 0 ≤ w_i ≤ 10⁹), where v_i and u_i — are the numbers of the nodes that are connected by the i-th edge, and w_i is its value. Note that the following condition must fulfill c_{v_i} ≠ c_{u_i}.

It is guaranteed that for any input data there exists at least one graph that meets these data. If there are multiple solutions, print any of them. You are allowed to print the edges in any order. As you print the numbers, separate them with spaces.

Sample Input:

Sample Output:

3 1 3
3 2 2

Sample Input:

Sample Output:

Informação

Provedor Codeforces

Código CF260D