n,t = map(int,input().split())
a = list(map(int,input().split()))
dp = []
for i in range(n+1):
    dp.append({})
dp[0][t] = 0
for i in range(n):
    for now, score in dp[i].items():
        for j in range(2):
            nxt = now & a[i]
            if j == 1:
                nxt = now | a[i]
            nxtscore = score + abs(now - nxt)
            if not (nxt in dp[i+1]) or dp[i+1][nxt] < nxtscore:
                dp[i+1][nxt] = nxtscore
print(max(dp[n].values()))