AtCoder Beginner Contest 084 D - 2017-like Number (区间问题 a[r]-a[l-1])

Problem Statement
We say that a odd number N is similar to 2017 when both N and (N+1)⁄2 are prime.


You are given Q queries.


In the i-th query, given two odd numbers li and ri, find the number of odd numbers x similar to 2017 such that li≤x≤ri.


Constraints
1≤Q≤105
1≤li≤ri≤105
li and ri are odd.
All input values are integers.
Input
Input is given from Standard Input in the following format:


Q
l1 r1
:
lQ rQ
Output
Print Q lines. The i-th line (1≤i≤Q) should contain the response to the i-th query.


Sample Input 1

1
3 7
Sample Output 1

2
3 is similar to 2017, since both 3 and (3+1)⁄2=2 are prime.
5 is similar to 2017, since both 5 and (5+1)⁄2=3 are prime.
7 is not similar to 2017, since (7+1)⁄2=4 is not prime, although 7 is prime.
Thus, the response to the first query should be 2.


Sample Input 2

4
13 13
7 11
7 11
2017 2017
Sample Output 2

1
0
0
1
Note that 2017 is also similar to 2017.


Sample Input 3
6
1 53
13 91
37 55
19 51
73 91
13 49
Sample Output 3

4
4
1
1
1

2

题意：判断[l,r]内与2017类似的数字，2017的性质：2017为素数，（2017+1）/2仍为素数。

思路：打表算出来1-10^5内各自的数字，然后结果为a[r]-a[l-1].（区间问题一直是我的一个弱项，类似于[l,r]找是3和7的倍数是多少个的问题，我在HNUST上WA了20发！！！！）

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