1775C - Interesting Sequence - CodeForces Solution

//Rakib Hasan

#include<bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
using    namespace __gnu_pbds;
using    namespace std;
#define file() freopen("input.txt","r",stdin);freopen("output.txt","w",stdout);
#define optimize()  ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);

#define mod  998244353 //1000000007
const long long infll=9000000000000000000;
const int inf = 2000000000;
const double eps=1e-9;


#define                    ll                   long long
#define                    pa                   pair<int,int>
#define                    ff                   first
#define                    ss                   second
#define                    pb                   push_back
#define                    PI                   acos(-1.0)
#define                    vi                   vector<int>
#define                    vll                  vector<ll>
#define                    yo                   cout<<"YES"<<endl
#define                    no                   cout<<"NO"<<endl
#define                    done                 cout<<ans<<endl
#define                    mem(a,b)             memset(a,b,sizeof(a))
#define                    minus                cout<<"-1"<<endl
#define                     duck                cout<<0<<endl
#define                    sqr(a)               ((a)*(a))
#define                    f(i,a,b)             for(int i=a;i<=(b);i++)
#define                    r(i,a,b)             for(int i=a;i>=(b);i--)
#define                    all(v)               v.begin(),v.end()
#define                    vpush(v,x)           int x; cin>>x; v.push_back(x);
#define                    mid(s,l)             (s+(l-s)/2)



//#define int long long


void solve()
{
   ll n,x;
   cin>>n>>x;
   if(n<x){
    cout<<-1<<endl;
    return;
   }
   if(n==x){
    cout<<n<<endl;
    return;
   }
   if(x==0){
    cout<<(1LL<<((ll)log2(n)+1LL))<<endl;
   }
   
   bitset<66>bn(n);
   bitset<66>bx(x);
   bool check=false;

   for(int i=0;i<=65;i++){
    if(bn[i]==1){
        if(bx[i]==0 and check){
            cout<<-1<<endl;
            return;
        }
        else if(bx[i]==1)check=true;
    }
    else if(bx[i]==1)check =true;
   }
    ll num=0;
    ll ans=n;
    ll last;


   for(int i=0;i<=65;i++){
    if(bx[i]==1){
        if(last==(1LL<<(ll)i)){
            cout<<-1<<endl;
            return;
        }
        ans+=(last-num);
        cout<<ans<<endl;
        return;
    }
    if(bn[i]==1){
        num+=(1LL<<(ll)i);
        last=(1LL<<((ll)i+1LL));

    }
   }


}

//signed main()
int main()
{
    optimize();
    int t;
    cin>>t;
    while(t--)
    {
     solve();
    }
}