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<algorithm>
#include<string>
#include<math.h>
#include<stdio.h>
#include<vector>
#include<map>
using namespace std;

string s;

int main() {
	cin >> s;

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

	return 0;
}