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>
#include<string.h>

int main(void){
	int cnt = 0;
  	char s[10];
	
  	rewind(stdin);
	scanf("%s",s);
  
  if(&s[0]==&s[1]){
  	cnt++;
  }
    if(&s[0]==&s[2]){
  	cnt++;
  }
    if(&s[0]==&s[3]){
  	cnt++;
  }
    if(&s[1]==&s[2]){
  	cnt++;
  }
    if(&s[1]==&s[3]){
  	cnt++;
  }
    if(&s[2]==&s[3]){
  	cnt++;
  }
  
  if(cnt == 2){
   printf("Yes");
  }else{
   printf("No");
  }
  
  return 0;

}