#include <bits/stdc++.h>
#define rep(i,a,b) for (int i=a; i<b; i++)
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(x) (x).begin(),(x).end()
#define debug printf
using namespace std;
typedef pair <int, int> PII;
typedef vector <int> VI;
typedef long long ll;
typedef long double ld;


int main ()
{
	int n, k;
	scanf ("%d %d", &n, &k);
	vector <int> mus(n);
	for (int &x: mus) scanf ("%d", &x);
	set <pair <int, int> > wor;
	int y =0;
	for (int x: mus) wor.insert(mp(x, y++));
	
	int b = 30;
	for (; b>=0; b--)
	{
		int ile = 0;
		for (int x: mus) if (x & (1<<b)) ile++;
		
		if (ile>=k) break;
	}
	
	int res = 0;
	for (; b>=0; b--)
	{
		vector <pair <int, int> > buf;
		for (auto x: wor) 
		{
			if ((x.fi & (1<<b)) ==0) buf.pb(x);
		}
		if ((int)wor.size() - (int)buf.size() <k) continue;
		for (auto x: buf) wor.erase(x);
		res+=(1<<b);
	}
	printf ("%d\n", res);
}