#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define ll long long
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define repl(i,a,b) for(ll i=(a);i<(b);i++)
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()

template <typename T> bool chmin(T &a,T b){if(a>b){a=b;return true;} return false;}
template <typename T> bool chmax(T &a,T b){if(a<b){a=b;return true;} return false;}


void solve(){
  ll n,m; cin >> n >> m;
  if(n<2*m){
    cout << 0 << "\n";
    return;
  }
  ll ok=0,ng=1e9;
  while(ng-ok>1){
    ll mid=(ok+ng)/2;
    ll b=m+(n-4*mid)/2*4;
    ll a=n-(n-4*mid)/2*2;
    if(b/2>=mid) ok=mid;
    else ng=mid;
  }
  cout << 3*ok << "\n";
  
  return;
}

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int T=1;
  cin >> T;
  while(T--) solve();
}