3205. Prime Gap

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
10
11
27
2
492170
0
Output
4
0
6
0
114

18 人解决,18 人已尝试。

20 份提交通过,共有 24 份提交。

2.8 EMB 奖励。

创建: 3 年,3 月前.

修改: 2 年,10 月前.

最后提交: 5 月,1 周前.

来源: Tokyo 2007

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