代码如下

#include <bits/stdc++.h>
using namespace std;
int n;

int zhishu(int num) {
	if (num == 1)
		return false;
	for (int i = 2; i <= sqrt(num); i++) {
		if (num % i == 0)
			return false;
	}
	return true;
}

int main() {
	cin >> n;
	if (n <= 3) {
		cout << "empty";
		return 0;
	}
	for (int i = 2; i <= n; i++) {
		if (zhishu(i) == 1 and zhishu(i + 2) == 1)
		cout << i <<  " " << i + 2 << endl;
	}


	return 0;
}