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: Wrong Answer)

#import math.sqrt as sqrt

#S = list(map(int, input().split()))
#B = list(map(int, input().split()))

S = list(input())
count = [0, 0, 0]

for i in range(len(S)-1):
    for j in range(i+1, len(S)):
        if S[i] == S[j]:
            count[i] += 1

       # print(S[j]+" "+S[i])

print(count)

if (count[0]==1 and count[1]==1) or (count[1]==1 and count[2]==1) or (count[2]==1 and count[0]==1):
    print("Yes")
else:
    print("No")