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 <stdlib.h>

int main()
{
    char x,c,z,y;
    scanf("%c %c %c %c",&x,&c,&z,&y);
    if(x==c&&x!=z&&x!=y){
        printf("Yes");
    }else if(c==z&&c!=x&&c!=y)
    {
        printf("Yes");
    }else if(z==x&&z!=c&&z!=y)
    {
        printf("Yes");
    }else if(y==x&&y!=c&&y!=z)
    {
        printf("Yes");
    }else if(x==""&&z==""&&c==""){
      printf("No");
    }else if(y==""&&z==""&&c==""){
      printf("No");
    }else if(x==""&&y==""&&c==""){
      printf("No");
    }else if(x==""&&z==""&&y==""){
      printf("No");
    }
   return 0;
}