代入样例2,其中一种边的数据是1 5

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

int main() {
	int n, sum = 0;
	cin >> n;
	for (int i = 1; i <= n / 2; i++) {
		for (int j = i; j <= n; j++) {
			cout << i << " " << j << endl;
			sum++;
		}
	}
	cout << sum;
	return 0;
}