#include <cstring>
#include <vector>
#include <stdio.h>
#include <bitset>
#include <string>
#include <cmath>
#include <algorithm>
#include <cstdlib>
#include<sstream>
#include <iomanip>
#include <vector>
#include<utility>
#include <iostream>
#define ll long long
using namespace std;
int main()
{

	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	ll t; cin >> t;
	while (t--) {
		ll x, y; cin >>x>> y;
		ll a = y / x;
		x = x * a;
		cout << x / 2<<"\n";
	}
}