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] #l = sorted(l,reverse=True) #i = l[0].find('1') ls = [] br = 0 for j in range(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) l = ls[:] ls=[] print(br)