/* 
*   @author:- MAHMUDUL HASAN SAKIB
*   DATE & TIME :- 2024-09-06 12:11:44
*   BANGLADESH , SYLHET.
*/ 

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <complex>
#include <deque>
#include <forward_list>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <optional>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
#define fi first
#define se second
#define endl '\n'
#define ll long long
#define ld long double
#define pb push_back
#define mp make_pair
#define vi vector<ll>
#define maxn 500005
#define mod 1000000007
#define inf 1000000007
#define pii pair<ll,ll>
#define vii vector<pii>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define lcm(a,b) ((a*b)/__gcd(a,b));
#define srt(v) sort(v.begin(),v.end())
#define rsrt(v) sort(v.rbegin(),v.rend())
#define rep(i, a, b) for(int i = (a); i < (b); i++)
#define per(i, a, b) for(int i = (a); i > (b); i--)
#define rev_str(str) reverse(str.begin(),str.end());
#define print(v) for(auto e:v) cout<<e<<" "; cout<<endl;
#define printp(v) for(auto e:v) cout<<e.first<<" "<<e.second<<endl;
#define fast ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);

void solve(){
    ll n,k;cin>>n>>k;
    if(n>=k){
        cout<<0<<endl;
    }
    else{
        ll what = k/n;
        ll  ki = what/2, bolo = (what+1)/2;
        ll mx=ki*(k-(n*ki));
        ll j= bolo*(k-(n*bolo));
        cout<<max(mx,j)<<endl;            
    }

}

int main() {
    //auto begin = std::chrono::high_resolution_clock::now();
    fast;
    ll t = 1;cin >> t;
    while (t--) {
        solve();
    }
    //auto end = std::chrono::high_resolution_clock::now();
    //auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
    //cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n";
    return 0;
}