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 <iostream>
#include <string>
#include <math.h>
#include <vector>
#include <algorithm>
#include <map>
using namespace std;
typedef long long cc;

cc a, b, c, Ans, i, j;
cc judge1=0, judge2=0, judge3;
string S;


int main() {
	cin >> S;
	for (i = 0; i < 3; i++) {
		for (j = i + 1; j < 4; j++) {
			if (S[i] == S[j])
				judge1 += 1;
		}
		if (judge1 == 1)
			judge2 += 1;
		judge1 = 0;
	}
	if(judge2==2)
		cout << "Yes" << endl;
	else
		cout << "No" << endl;

		return 0;
	}