import sys


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    n, k = map(int, input().split())
    a = sorted(map(int, input().split()), reverse=True)
    c = [k]
    for v in a[:-1]:
        c += [i % v for i in c]

    return max(i % a[-1] for i in c)


if __name__ == '__main__':
    ret = main()
    if ret is not None:
        print(ret)