n, m = map(int, input().split())
a = list(map(int, input().split()))
ans = 0
for i in range(1, m):
	d = a[i] - a[i - 1]
	x = d
	p = 1
	while x >= 4 and x % 2 == 0:
		x //= 2
		p *= 2
	ans += d - p
print(ans)