CF755A.PolandBall and Hypothesis

普及/提高-

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题目描述

PolandBall is a young, clever Ball. He is interested in prime numbers. He has stated a following hypothesis: "There exists such a positive integer $n$ that for each positive integer $m$ number $n·m+1$ is a prime number".

Unfortunately, PolandBall is not experienced yet and doesn't know that his hypothesis is incorrect. Could you prove it wrong? Write a program that finds a counterexample for any $n$ .

输入格式

The only number in the input is $n$ ( $1<=n<=1000$ ) — number from the PolandBall's hypothesis.

输出格式

Output such $m$ that $n·m+1$ is not a prime number. Your answer will be considered correct if you output any suitable $m$ such that $1<=m<=10^{3}$ . It is guaranteed the the answer exists.

输入输出样例

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

说明/提示

A prime number (or a prime) is a natural number greater than $1$ that has no positive divisors other than $1$ and itself.

For the first sample testcase, $3·1+1=4$ . We can output $1$ .

In the second sample testcase, $4·1+1=5$ . We cannot output $1$ because $5$ is prime. However, $m=2$ is okay since $4·2+1=9$ , which is not a prime number.

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