import sys
input = sys.stdin.readline

from collections import deque

N=int(input())
A=list(map(int,input().split()))

Q=deque(A)

for i in range(1,N+1):
    if Q[0]<=i:
        Q.popleft()
    elif Q[-1]<=i:
        Q.pop()

if len(Q)==0:
    print("Yes")
else:
    print("No")