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 PyPy3 (2.4.0) (judge verdict: Accepted)

S = input().strip()
C = {}
for i in range(4):
    a = S[i]
    if a not in C:
        C[a] = 0
    C[a] += 1
C = list(C.items())
if len(C)==2 and C[0][1]==2:
    print("Yes")
else:
    print("No")