#include <bits/stdc++.h>
using namespace std;
#define ll long long 
#define N 500010
ll n, m, a[N], flag[N], ans;
//flag数组为断点标记数组
int main() {
    ll i, j;
    cin >> n >> m;
    for (i = 1; i <= n; i++) {
        cin >> a[i];
    }
    for (j = 62; j >= 0; j--) {
        ll tmp = 0, sum = 0;
        for (i = 1; i <= n; i++) {
            tmp ^= (a[i] >> j) & 1;
            //判断第j位的异或和是否为1
            if (!tmp && !flag[i]) sum++;
            //同时要保证不与高位冲突
        }
        if ((tmp & 1) || (sum < m)) {
            //如果该位最终结果为1，或者不能分成超过M段
            ans += 1LL << j;
            continue;
        }
        tmp = 0;
        //将第j位的断点标记加上去
        for (i = 1; i <= n; i++) {
            tmp ^= (a[i] >> j) & 1;
            if (tmp && !flag[i]) flag[i] = 1;
        }
    }
    cout << ans;
    return 0;
}