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 C (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#define N 100010
int sosu(int a)
{
  for(int j=2;j <= a-1 ;j++){
    if(a%j == 0) return 0;
  }
  return 1;
}
int main(void)
{
  int ss[N+1],tmp[N+1],tmp1[N+1];
  tmp[0]=tmp[1]=tmp[2]=0;
  tmp1[0]=tmp1[1]=tmp1[2]=0;
  ss[0]=ss[1]=0;
  ss[2]=1;
  for(int i=3;i<=N;i++){
    //2n
    if(i%2 == 0){
      ss[i]=0;
      tmp1[i]=0;
    //2n+1
    }else{
      ss[i]=sosu(i);
      if((ss[i]==1)&&(ss[(i+1)/2]==1)){
        tmp1[i]=1;
      }else tmp1[i]=0;
    }
    tmp[i]=tmp[i-1]+tmp1[i];
  }
  int q;
  scanf("%d",&q);
  int l[q],r[q],ans[q];
  for(int i=0;i<q;i++){
    scanf("%d%d",&l[i],&r[i]);
    ans[i]=tmp[r[i]]-tmp[l[i]-1];
  }
  //printf("%d\n",tmp[99291]);
  for(int i=0;i<q;i++) printf("%d\n",ans[i]);
  return 0;
}