Problem:
Score : 100 points

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.

Constraints

The length of S is 4.

S consists of uppercase English letters.

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.

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

Solution in Lua (5.3.2) (judge verdict: Accepted)

local s = io.read("l")
local a, b, c, d = string.byte(s, 1, 4)
if ((a == b) and (c == d)) or
   ((a == c) and (b == d)) or
   ((a == d) and (b == c)) then
   if (a == b) and (a == c) then
       print("No")
   else
       print("Yes")
   end
else
   print("No")
end