Nikita and stack

## 题目描述 NK有一个栈。 此问题中的栈是支持两个操作的数据结构。 push(x)操作将整数$x$放在栈顶，而pop()操作则从栈中删除顶部的整数，即最后添加的整数。 如果栈为空，则pop()函数不执行任何操作。 NK用堆栈进行了$m$次操作，但忘记了那$m$次操作干了什么。在第$i$个步骤中，他记得他进行过第$p_{i}$个操作。 换句话说，他以某些排列$p_{1}$，$p_{2}$，...，$p_{m}$的顺序记住操作。 在完成每一步之后，NK想要以相应的顺序知道在已经记住的操作后栈的顶部的数是什么。帮帮NK！ ## 输入格式 第一行是一个整数$m(1\le m\le 10^{5})$，表示NK进行了几次操作。 接下来的$m$行是NK所记得的操作。第$i$行包含2个整数，$p_i$和$t_i$$(1\le p_i\le m, t_i = 0$或$t_i = 1)$———他在步骤i上记住的操作索引以及操作类型。若$t_i=0$，则该操作为pop()，反之为push(x)。如果操作为push(x)，则该行还会包含一个整数$x_i(1\le x_i\le10^6)$，即加到栈内的数。 确保从1到$m$的每个整数在整数$p_{i}$中仅出现一次。 ## 输出格式 输出$m$个整数。第$i$个输出的整数应等于NK记得的第$i$次操作后栈顶的元素。如果栈为空，则返回$-1$。 ## 说明/提示 在第一个示例中，在NK记住第一步的操作之后，操作push(2)是唯一的操作，因此答案是2。 在他记住在push(2)之前完成的pop()操作之后，答案保持不变。 在第二个示例中，操作是push(2)，push(3)和pop()。 NK按照顺序记住它们。 在第三个示例中，NK以相反的顺序记住了所有的操作。

Nikita has a stack. A stack in this problem is a data structure that supports two operations. Operation push(x) puts an integer $ x $ on the top of the stack, and operation pop() deletes the top integer from the stack, i. e. the last added. If the stack is empty, then the operation pop() does nothing. Nikita made $ m $ operations with the stack but forgot them. Now Nikita wants to remember them. He remembers them one by one, on the $ i $ -th step he remembers an operation he made $ p_{i} $ -th. In other words, he remembers the operations in order of some permutation $ p_{1},p_{2},...,p_{m} $ . After each step Nikita wants to know what is the integer on the top of the stack after performing the operations he have already remembered, in the corresponding order. Help him!

The first line contains the integer $ m $ ( $ 1<=m<=10^{5} $ ) — the number of operations Nikita made. The next $ m $ lines contain the operations Nikita remembers. The $ i $ -th line starts with two integers $ p_{i} $ and $ t_{i} $ ( $ 1<=p_{i}<=m $ , $ t_{i}=0 $ or $ t_{i}=1 $ ) — the index of operation he remembers on the step $ i $ , and the type of the operation. $ t_{i} $ equals $ 0 $ , if the operation is pop(), and $ 1 $ , is the operation is push(x). If the operation is push(x), the line also contains the integer $ x_{i} $ ( $ 1<=x_{i}<=10^{6} $ ) — the integer added to the stack. It is guaranteed that each integer from $ 1 $ to $ m $ is present exactly once among integers $ p_{i} $ .

Print $ m $ integers. The integer $ i $ should equal the number on the top of the stack after performing all the operations Nikita remembered on the steps from $ 1 $ to $ i $ . If the stack is empty after performing all these operations, print -1.

2
2 1 2
1 0

2
2

3
1 1 2
2 1 3
3 0

2
3
2

5
5 0
4 0
3 1 1
2 1 1
1 1 2

-1
-1
-1
-1
2

In the first example, after Nikita remembers the operation on the first step, the operation push(2) is the only operation, so the answer is $ 2 $ . After he remembers the operation pop() which was done before push(2), answer stays the same. In the second example, the operations are push(2), push(3) and pop(). Nikita remembers them in the order they were performed. In the third example Nikita remembers the operations in the reversed order.