sutcu.cpp

#include "bits/stdc++.h"

using namespace std;
typedef __int128_t lint;
typedef __uint128_t ulint;
#define mod(x) x%1000000007
long long int n,mm;
lint tot = 0;
lint bits[64];

#define IsBitSet(num,bit) ((num >> bit) &1ULL)



std::ostream&
operator<<( std::ostream& dest, __int128_t value )
{
    std::ostream::sentry s( dest );
    if ( s ) {
        __uint128_t tmp = value < 0 ? -value : value;
        char buffer[ 128 ];
        char* d = std::end( buffer );
        do
        {
            -- d;
            *d = "0123456789"[ tmp % 10 ];
            tmp /= 10;
        } while ( tmp != 0 );
        if ( value < 0 ) {
            -- d;
            *d = '-';
        }
        int len = std::end( buffer ) - d;
        if ( dest.rdbuf()->sputn( d, len ) != len ) {
            dest.setstate( std::ios_base::badbit );
        }
    }
    return dest;
}


int main ()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> n >>mm;
    lint m = mm;
    unsigned long long int x = 0;
    for(int i =0; i<n; i++)
    {
        cin >> x;
        for(int j =0; j< 64; j++)
        {
            bits[j] += IsBitSet(x,j);
        }
        tot += x;
    }
    unsigned long long int res = 0;
    for(int j = 0; j < 64; j++)
    {
        bits[j] = (n - bits[j]) - bits[j];
        // cout <<"j: "<<j << " bits j: " <<bits[j] << endl;;
        if(bits[j] <= 0) 
        {
             
            res += (((unsigned long long int)1)<<j);
            tot += bits[j]*(((lint)1)<<j);
        }
    }
    if(tot > m)
    {
        cout << -1;
        return 0;
    }

    // cout << res  << endl;

    for(lint j =63; j >=  0; j--)
    {
        if(bits[j] <= 0) continue;

        // cout << "j: "<<j << endl;
        // cout << "tot: " << tot << endl;
        // cout << "bits[j]*(1<<j): " << bits[j]*(((lint)1)<<j) << endl;

        if(tot + bits[j]*(((lint)1)<<j) <= (lint) m)
        {
            tot += bits[j]*(((lint)1)<<j);
            res += (((unsigned long long int)1)<<j);
        }
    }

    cout << res;
    return 0;
}