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题目描述

A queue (FIFO structure) can be implemented by two stacks (LIFO structure) in the following way:

1. Start from two empty stacks $s_1$ and $s_2$.
2. When element $e$ is enqueued, it is actually pushed onto $s_1$.
3. When we are supposed to dequeue, $s_2$ is checked first. If $s_2$ is empty, everything in $s_1$ will be transferred to $s_2$ by popping from $s_1$ and immediately pushing onto $s_2$. Then we just pop from $s_2$ -- the top element of $s_2$ must be the first one to enter $s_1$ thus is the first element that was enqueued.

Assume that each operation of push or pop takes 1 unit of time. You job is to tell the time taken for each dequeue.

输入格式

Each input file contains one test case. For each case, the first line gives a positive integer $N$ ($\le 10^3$), which are the number of operations. Then $N$ lines follow, each gives an operation in the format

Operation Element

where Operation being I represents enqueue and O represents dequeue. For each I, Element is a positive integer that is no more than $10^6$. No Element is given for O operations. It is guaranteed that there is at least one O operation.

输出格式

For each dequeue operation, print in a line the dequeued element and the unites of time taken to do this dequeue. The numbers in a line must be separated by 1 space, and there must be no extra space at the beginning or the end of the line. In case that the queue is empty when dequeue is called, output in a line ERROR instead.

样例

10
I 20
I 32
O
I 11
O
O
O
I 100
I 66
O

20 5
32 1
11 3
ERROR
100 5

限制

对于所有的测试用例,限制为400ms, 64MB