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 Python (3.4.3) (judge verdict: Runtime Error)

n = int(input())
p = [int(_) for _ in input().split()]

cnt = 0
for i in range(0, n-2):
    print(p[i], p[i+1], p[i+2])
    if (p[i] < p[i+1] < p[i+2]) or (p[i] > p[i+1] > p[i+2]):
        cnt += 1
print(cnt)