N,K=map(int,input().split())
A=list(map(int,input().split()))
A.sort()
L=[K]
for i in range(N-1,0,-1):
	a=A[i]
	for x in L[:]:
		if x>a:
			L.append(x%a)
ans=0
for x in L:
	alt=x%A[0]
	if ans<alt:
		ans=alt
print(ans)