N = int(input())
A = [0] + list(map(int,input().split()))
maxN = N + 1
flag = 1
while flag == 1:
    flag = 0
    maxNt = maxN
    for i in reversed(range(1,maxN)):
        if flag == 0:
            if i == 1 and A[i] == 0:
                flag = 2
                break
            elif A[i] == 0:
                dummy = 0
            elif A[i] != i:
                break
            else:
                flag = 1
            maxNt = i + 1
        if flag == 1:
            if A[i] == i:
                if i == 1:
                    A[i] = 0
                elif A[i-1] != i - 1:
                    A[i-1] += 1
                    A[i] = 0

    maxN = maxNt
    if flag == 2:
        break

if flag == 0:
    print("No")
else:
    print("Yes")