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: Runtime Error)

N=int(input())
num = list(map(int, input().strip().split()))

count = 0
for i in range(N-2):
    if((num[i]<num[i+1]<num[i+2])or(num[i]>num[i+1]>num[i+2])):
        count +=1
print(count)