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<bits/stdc++.h> //ABC 132_a
using namespace std;
char str[5];
int main() {
    for(int i=1;i<=4;i++){
    	cin>>str[i];
    	
	}
	if((str[1]==str[2])&&(str[3]==str[4])&&(str[1]!=str[3])||(str[1]==str[3])&&(str[2]==str[4])&&(str[1]!=str[2])||(str[1]==str[4])&&(str[2]==str[3])&&(str[1]!=str[2])){
		cout<<"Yes";
	}
    else{
      	cout<<"No";
	}
    return 0;
}