Score : 100 points
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 is given from Standard Input in the following format:
S
If S consists of exactly two kinds of characters which both appear twice in S, print Yes
; otherwise, print No
.
ASSA
Yes
S consists of A
and S
which both appear twice in S.
STOP
No
FFEE
Yes
FREE
No