时间限制：C/C++/Rust/Pascal 1秒，其他语言2秒
空间限制：C/C++/Rust/Pascal 256 M，其他语言512 M
64bit IO Format: %lld
题目描述
AFei has many cards. Each card has a number written on it. Now he wants to takes some out of his card and puts them in a box. And he wants to know whether the card with the number x was in the box. So he has the following two operations：
- 0 x （It means to put a card with the number x in the box.）
- 1 x (It means to query if there is a card with the number x in the box.)
输入描述:
The first line of the input is an integer n (1 <= n <= 106), the number of operations. Next n lines represent n operations, and two integers k ( k∈{0,1}) and x (0<=x<=109) are separated by spaces on each line, as described above.
输出描述:
For each query, output one line "yes" if there is a card with the number x in the box, otherwise output one line "no".