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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;

int main(int argc, char** argv){
  string S;
  cin >> S;
  
  int tmp = 0;
  for(int cnt0=0; cnt0<4; cnt0++){
    tmp = count(S.begin(), S.end(), S[cnt0]);
    if(tmp != 2) {
      cout << "No" << endl;
      return 0;
    }
  }
  
  cout << "Yes" << endl;
  return 0;
  
  
}