Problem #3205 - ECNU Online Judge

单点时限: 8.0 sec

内存限制: 256 MB

The sequence of $n - 1$ consecutive composite numbers (positive integers that are not prime and not equal to $1$ ) lying between two successive prime numbers $p$ and $p + n$ is called a prime gap of length $n$ . For example, $(24, 25, 26, 27, 28)$ between $23$ and $29$ is a prime gap of length $6$ .

Your mission is to write a program to calculate, for a given positive integer $k$ , the length of the prime gap that contains $k$ . For convenience, the length is considered $0$ in case no prime gap contains $k$ .

输入格式

The input is a sequence of lines each of which contains a single positive integer. Each positive integer is greater than $1$ and less than or equal to the $100000$ -th prime number, which is $1299709$ . The end of the input is indicated by a line containing a single zero.

输出格式

The output should be composed of lines each of which contains a single non-negative integer. It is the length of the prime gap that contains the corresponding positive integer in the input if it is a composite number, or $0$ otherwise. No other characters should occur in the output.

样例

Input

Output

35 人解决，37 人已尝试。

38 份提交通过，共有 56 份提交。

2.9 EMB 奖励。

创建: 7 年，11 月前.

修改: 7 年，5 月前.

最后提交: 4 月，3 周前.

来源: Tokyo 2007

基本算法循环数组

3205. Prime Gap

输入格式

输出格式

样例

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