n,k=[int(i) for i in input().split()]
d=[int(i) for i in input().split()]

def hist(d):
    h=[[] for _ in range(32)]
    for i in range(len(d)):
        for j in range(32):
            if d[i] & (2**j):
                h[j].append(d[i])
    return h

v = hist(d)
r = 0
for i in range(31, 0, -1):
    if len(v[i]) >= k:
        h = hist(v[i])
        for j in range(len(h[i]), 0, -1):
            if len(h[j]) >= k:
                r += 2 ** j
        break

print(r)