## Problem Description

Oaiei is now studying Compiler Principles. He finds that compilers must convert each of the statement into a syntax tree for analysis.

A syntax tree is a binary tree. Its leaf node is a variable or is a numerical and each internal node is an operator.

Now your task is, given a syntax tree, convert it into a statement.

Each leaf node is only a letter (a-z or A-Z) or a number (0-9). Operators can only be one of =, +, -, x, / and %.

It’s simple, isn’t it?

## Input

The input consists of several test cases. For each case, the first line has an integer n (1<=n<=101), indicating the number of nodes in the given syntax tree, nodes are numbered 1, 2, ..., n.
Next n lines, each line consists of three integers A,B,C, indicating the node numbered A has a left child numbered B, a right child numbered C. 0 indicates the node doesn’t have a left or right child. Following C, there is a character D, indicating the value of the node.
All nodes are given in layer order.

## Output

The statement after coverting the syntax tree. No blanks allowed.
(The conversion order is left subtree first and then right subtree)

## Sample Input

7
1 2 3 =
2 0 0 a
3 4 5 +
4 0 0 b
5 6 7 +
6 0 0 c
7 0 0 d

## Sample Output

a=b+c+d

## Source

FOJ月赛-2007年6月