N,K = list(map(int,input().split())) l = list(map(int,input().split())) for i in range(N): l[i]=bin(l[i])[2:] l[i]='0'*(30-len(l[i]))+l[i] ls = [] br = 0 k = max(l) a = k.find('1') for j in range(a,30): for i in range(len(l)): if str(l[i])[j]=='1': ls.append(l[i]) if len(ls)>=K: br+=2**(30-j-1) if len(ls)>K: l = ls[:] ls=[] print(br,end='')