Prime Visits Question:I am not able to find the error in my code. One test case is showing TLE and other is showing wrong. I am not able to understand the solution as well. Please help

#1

import java.util.*;
public class Main {
public static Scanner scn = new Scanner(System.in);
public static void main(String args[]) {
int n = scn.nextInt();

	for(int i=0; i<n; i++)
	{
		int a = scn.nextInt();
		int b = scn.nextInt();
		nOfPrime(a,b);
	}
}

public static void nOfPrime(int a, int b)
{
	int count=0;
	
	for(int i=a; i<=b; i++)
	{
		boolean flag = true;
		if(i==1)
		flag = false;

		for(int j=2; j*j<=i; j++)
		{
			if(i%j==0)
			{
				flag = false;
				break;
			}
		}
		if(flag==true)
		count++;
	}
	System.out.println(count);
}

}

#2

To overcome TLE, use Sieve. And wrong answer is probably due to some corner cases. Hard code them.

#3

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