#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
ll n, k;
bool b[300005];
bool c[300005][31];
ll po[31];
ll x, ans;
set<ll>s[31];
int main()
{
    ios_base::sync_with_stdio(false);
    cin>>n>>k;
    po[0]=1;
    for (ll i=1; i<=30; ++i)
    {
        po[i]=po[i-1];
        po[i]*=2;
    }
    for (ll i=1; i<=n; ++i)
    {
        b[i]=true;
        cin>>x;
        ll j=0;
        while(x)
        {
            if (x%2) s[j].insert(i);
            ++j;
            x/=2;
        }
    }
    for (ll i=30; i>=0; --i)
    {
        if (s[i].size()>=k)
        {
            ans+=po[i];
            for (auto z: s[i])
            {
                c[z][i]=true;
            }
            for (ll j=1; j<=n; ++j)
            {
                if (b[j] && !c[j][i])
                {
                    b[j]=false;
                    for (ll p=i-1; p>=0; --p)
                    {
                        s[p].erase(j);
                    }
                }
            }
        }
    }
    cout<<ans;
}