Problem Statement

You are given a 4-character string S consisting of uppercase English letters.
Determine if S consists of exactly two kinds of characters which both appear twice in S.

Input

Input is given from Standard Input in the following format:
S

Output

If S consists of exactly two kinds of characters which both appear twice in S, print Yes; otherwise, print No.

Constraints

• The length of S is 4.
• S consists of uppercase English letters.

Sample Input 1

ASSA

Sample Output 1

Yes

S consists of A and S which both appear twice in S.

Sample Input 2

STOP

Sample Output 2

No

Sample Input 3

FFEE

Sample Output 3

Yes

Sample Input 4

FREE

Sample Output 4

No

见题面 Input 部分

见题面 Output 部分