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<stdio.h>
#include<string>
using namespace std;

int main() {
	char S[] = "    ";

	cin >> S[1] >> S[2] >> S[3] >> S[4];


	if (S[1] == S[2] && S[3] == S[4] || S[1] == S[3] && S[2] == S[4] || S[1] == S[4] && S[2] == S[3]) {
		cout << "Yes" << endl;
	}
		
	else {
		cout << "No" << endl;
	}
		
	return 0;
}