n, t = map(int, input().split())
A = list(map(int, input().split()))

dp = {t:0}
for a in A:
    ndp = {}
    for k, v in dp.items():
        nk = k & a
        nv = v + abs(nk - k)
        ndp[nk] = max(ndp.get(nk, 0), nv)
        nk = k | a
        nv = v + abs(nk - k)
        ndp[nk] = max(ndp.get(nk, 0), nv)
    dp = ndp
print(max(dp.values()))