Problem Statement

Snuke is about to make an integer sequence of length N consisting of 0 and 1.
He starts with an empty sequence x and does the following two kinds of operations N times in total, in any order he likes.

• Operation A: Flip every element of x, that is, convert each 0 to 1 and vice versa. Then, add 0 to the beginning of x.
• Operation B: Add 0 to the end of x.

You are given an integer sequence of length N consisting of 0 and 1: $A=(A_1,A_2,\cdots,A_N)$.
Determine whether it is possible to make x equal to A.

Input

Input is given from Standard Input in the following format:
N
$A_1 A_2 \cdots A_N$

Output

If it is possible to make x equal to A, print Yes; otherwise, print No.

Constraints

• $1 \leq N \leq 2 \times 10^5$
• $0 \leq A_i \leq 1$
• All values in input are integers.

Sample Input 1

4
0 1 1 0

Sample Output 1

Yes

Snuke can do the following.

• Start with x=()
• Do operation A, making x=(0).
• Do operation B, making x=(0,0).
• Do operation A, making x=(0,1,1).
• Do operation B, making x=(0,1,1,0).

Sample Input 2

4
1 0 0 0

Sample Output 2

No

Sample Input 3

4
0 0 0 1

Sample Output 3

No

见题面 Input 部分

见题面 Output 部分