#include <iostream>
#include <vector>
using namespace std;

int main(){
    int N, K;
    cin >> N >> K;
    vector<int> codes(N);
    bool status1=  false;
    bool status0[30];
    for (int i = 0; i < 30; i++)
    {
        status0[i] = false;
    }
    
    vector<bool *> status(N, &status1);
    int sum=0;
    for (int i = 0; i < N; i++)
    {
        cin >> codes[i];
    }
    for (int i = 29; i >=0; --i)
    {
        int count = 0;
        for (int j = 0; j < N; ++j)
        {
            if(!*status[j]){
                if((codes[j]>>i)&1){
                    count++;
                }
                else{
                    status[j] = status0+i;
                }
            }
        }
        if(count>= K){
            sum+=1<<i;
            status0[i] = true;
        }
        
    }
    cout << sum << endl;
    
    
    return 0;
}