d613.
Prime Gap

Content

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 .

Input

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 100000th prime number, which is 1299709. The end of the input is indicated by a line containing a single zero.

Output

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.

Sample Input
#1

10 11 27 2 492170 0

Sample Output
#1

4 0 6 0 114

測資資訊：

記憶體限制：
512
MB

公開 測資點#0 (100%): 1.0s , <1M

公開 測資點#0 (100%): 1.0s , <1M