Composites and Primes Sieve of Eratosthenes dp

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/*

Given two integers L and R find the difference of number of composites and primes between the range L and R (both inclusive).
Input:
First line of input contains of an integer 'T' denoting number of test cases . Then T test cases follow.
Each test contains two integers L and R .

Output:
For each case print an integer corresponding to the answer .

Constraints:
1<=T<=100
1<=L<=R<=10^7

Example:

Input:
2
4 4
4 6
Output:
1
1
*/
// given l , r print no of comp- no of prime  T.C->0.21
// normal approac i*i<=n gives TLE > 3.14
#include<bits/stdc++.h>
using namespace std;
bool prime[100001];
void SieveOfEratosthenes()
{
    memset(prime, true, sizeof(prime));
    prime[0]=false;
    prime[1]=false;
    for (int p=2; p*p<=10000000; p++)
    {
   
        if (prime[p] == true) // we make all multiples of prime false
        {
            for (int i=p*p; i<=10000000; i += p)  // we make all multiples of prime false
                prime[i] = false;
        }
    }
}
bool checkPrime(int num){
    return prime[num];
}

int main() {
//code
SieveOfEratosthenes();
    int t;
    cin>>t;
    while(t--){
        int l,r;
        cin>>l>>r;
     
        int cn=0,pn=0;
     
        for(int i=l;i<=r;i++){
            if(checkPrime(i) && i>1){
             
               pn++;
            }else{
                if(i>1){
                    cn++;
                }
             
            }
        }
     
        cout<<(cn-pn)<<endl;
     
    }
   return 0;
}

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