from sys import exit
n = int(input())
a = list(map(int, input().split()))

s = sum(a)
for _ in range(s):
	for i, x in enumerate(a):
		if x == i+1:
			cur = i
			a[cur] = 0
			break
	else:
		print("No")
		exit()
	for i in range(cur-1, -1, -1):
		a[i] += 1

print("Yes")