设当前系统中有多个栈在工作，多栈模拟问题要求模拟当前系统中各栈的工作状态。

由文件input.txt给出输入数据。第1行是正整数n，表示有n个栈操作。接下来的n行，

每行给出一个栈操作指令。栈操作指令“PUSH A B”表示将正整数B加入编号为A的栈顶；

栈操作指令“POP A”表示输出编号为A的栈顶元素输入文件示例 输出文件示例

input.txt output.txt

7

PUSH 1 100

PUSH 1 200

PUSH 2 300

PUSH 2 400

POP 3

POP 1

POP 2

0

200

4-set up the current system in a number of warehouse work, Stack simulation requires simulation of the current system of state stack. Input.txt documents presented by the input data. Line 1 is a positive integer n, n-stack operation. N the next trip, each trip is a stack operating instructions. Stack operating instructions "PUSH A B" is said to integer numbers of B to A stack; Stack operating instructions "A POP," said output No. A stack of documents imported elements example output file example inpu t.txt 1100 output.txt 7 PUSH PUSH PUSH 1200 2300 PUSH 2400 POP POP a POP 3 2 0200 4