Problem:
Score : 400 points

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 l_i and r_i, find the number of odd numbers x similar to 2017 such that l_i ≤ x ≤ r_i.

Constraints

1≤Q≤10^5

1≤l_i≤r_i≤10^5

l_i and r_i are odd.

All input values are integers.

Input

Input is given from Standard Input in the following format:

Q
l_1 r_1
:
l_Q r_Q

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

Solution in Python (3.4.3) (judge verdict: Accepted)

import bisect


def eratosthenes_generator():
    n = 3
    h = {}
    while True:
        m = n
        if n in h:
            b = h[n]
            m += 2 * b
            while m in h:
                m += 2 * b
            h[m] = b
            del h[n]
        else:
            m += 2 * n
            while m in h:
                m += 2 * n
            h[m] = n
            yield n
        # print(n, h)
        n += 2


ps = {2}
like2017s = [3]
for p in eratosthenes_generator():
    if p % 4 == 1 and (p + 1) // 2 in ps:
        like2017s.append(p)
    ps.add(p)
    if p >= 1e5:
        break
# print(like2017s)

q = int(input())
buf = []
for l, r in (map(int, input().split()) for _ in range(q)):
    li = bisect.bisect_left(like2017s, l)
    ri = bisect.bisect(like2017s, r)
    # if like2017s[li] == l:
    #     li -= 1
    buf.append(ri - li)
    # print(li, ri)
print('\n'.join(map(str, buf)))