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: Wrong Answer)

#include <iostream>
#include <string>
using namespace std;

int main() {
  string s;
  cin >> s;

  int cnt[4];
  for(int i = 0; i < s.size(); i++) {
    for(int j = 0; j < s.size(); j++) {
      if(s[j] == s[i]) cnt[i]++;
    }
  }

  int judge = 0;
  for(int i = 0; i < 4; i++) {
    if(cnt[i] == 2) judge++;
  }

  if(judge == 8) cout << "Yes";
  else cout << "No";
}