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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include <iostream>
#include <algorithm>

using namespace std;

#define fori(x) for (int i = 0; i < x; ++i)
#define forj(x) for (int j = 0; j < x; ++j)

int main() {
    char s[4];
	cin >> s;
    sort(s,s+4);
    if((s[0]==s[1])&&(s[2]==s[3])){
        cout<<"Yes";
    }else{
        cout<<"No";
    }
	return 0;
}