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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int main(void) {
    int cnt =0;
    int cnt2 =0;
    char temp;
	char a[4];
	for(int i = 0;i < 4;i++){
	    scanf("%c",&a[i]);
	}
	for(int i = 0;i< 4;i++){
	    
	   if(a[0] != a[i]){
	       cnt2++;
	   }
	    
	    
	}
	
    if(cnt2 == 2){
        printf("Yes");
    }else{
        printf("No");
    }
	return 0;
	
}