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<bits/stdc++.h>

using namespace std;

int main()
{
/*string s;
string t;

cin>>s;
cin>>t;
int contador=0;
for(int i=0;i<3;i++)
{
	if(s[i]==t[i])
	{
		contador=contador+1;
	}
	
	
}
cout<<contador;*/
string s;
cin>>s;
sort(s.begin(),s.end());

if((s[0]==s[1])&&(s[2]==s[3]))
{
	cout<<"YES"<<endl;
	
}
else
{
	cout<<"NO"<<endl;
}


return 0;


}