求大佬调试

#include <iostream>

using namespace std;

int IsPrimer(int start)
{
	bool flag = true;
	for(int i = 3; i*i <= start; i += 2)
	{
		if(start % i == 0)
		{
			flag = false;
			
			break;
		}
	}
	
	if(!flag) 
		return IsPrimer(start + 2);
	else
		return start;
}

int main()
{
	int n = 0; cin >> n;
	
	if(n < 5) cout << "empty" << endl;
	
	int FirstPrimer = 3, NextPrimer = 5;
	
	while(NextPrimer <= n)
	{
		if(NextPrimer - FirstPrimer == 2) cout <<  FirstPrimer << ' ' << NextPrimer << endl;
		
		FirstPrimer = IsPrimer(NextPrimer);
		NextPrimer = IsPrimer(FirstPrimer + 2);
	}
	
	return 0;
}