d613. Prime Gap
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最近更新 : 2011-08-30 09:12

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
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出處:
ICPC [管理者: electron (電子) ]

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ID User Problem Subject Hit Post Date
24325 hshua (hshua) d613
題意
647 2021-02-06 17:56