Untitled

#include <bits/stdc++.h>
using namespace std;
#define ll long long
int tt, tc;

void solve() {
    int n;
    ll x;
    cin >> n >> x;
    vector<ll> a(n);
    for (ll& u : a) cin >> u;

    ll xoring = 0, anding = (1LL << 40) - 1;
    for (ll u : a) {
        xoring ^= u;
        anding &= u;
    } 

    int operations = 0;
    if (xoring >= x) {
        cout << 0 << "\n";
        return;
    }
    for (int bit = 31; bit >= 0; --bit) {
        if (((1LL << bit) & xoring) == 0) {
            if (((1LL << bit) & anding) == 0) {
                xoring |= (1LL << bit);
                operations++;
            }
        }
        if (xoring >= x) {
            cout << operations << "\n";
            return;
        }
    }
    cout << -1 << "\n";
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    tt = 1, tc = 1; // cin >> tt;
    while (tt--) solve(), tc++;
}