CF1165B.Polycarp Training

普及/提高-

通过率：0%

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题目描述

Polycarp wants to train before another programming competition. During the first day of his training he should solve exactly $1$ problem, during the second day — exactly $2$ problems, during the third day — exactly $3$ problems, and so on. During the $k$ -th day he should solve $k$ problems.

Polycarp has a list of $n$ contests, the $i$ -th contest consists of $a_i$ problems. During each day Polycarp has to choose exactly one of the contests he didn't solve yet and solve it. He solves exactly $k$ problems from this contest. Other problems are discarded from it. If there are no contests consisting of at least $k$ problems that Polycarp didn't solve yet during the $k$ -th day, then Polycarp stops his training.

How many days Polycarp can train if he chooses the contests optimally?

输入格式

The first line of the input contains one integer $n$ ( $1 \le n \le 2 \cdot 10^5$ ) — the number of contests.

The second line of the input contains $n$ integers $a_1, a_2, \dots, a_n$ ( $1 \le a_i \le 2 \cdot 10^5$ ) — the number of problems in the $i$ -th contest.

输出格式

Print one integer — the maximum number of days Polycarp can train if he chooses the contests optimally.

输入输出样例

输入#1
```
4
3 1 4 1
```
输出#1
```
3
```
输入#2
```
3
1 1 1
```
输出#2
```
1
```
输入#3
```
5
1 1 1 2 2
```
输出#3
```
2
```

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