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 9.2.1) (judge verdict: Accepted)

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
#include<string.h>
#define BUFSIZE 1000000




int main(void){
char s[BUFSIZE];
scanf("%s",s);
int cnt =0 ;
char rem;

for(int i = 0 ;i < 4;i++){
  for(int j = 0;j < 4;j++){
    if(i == j)  break;
    if(s[i] == s[j]){
    if(s[i] == rem){
      printf("No");
      exit(0);
    }
      cnt++;
      rem = s[i];
      break;
    }

  }

}

if(cnt == 2) printf("Yes");
else printf("No");

return 0;



}