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){
  char str[5];
  int i;
  for(i=1;i<5;i++)
    scanf("%c",&str[i]);
  if(str[0]==str[1]||str[0]==str[2]||str[0]||str[3]||str[2]==str[1]||str[1]==str[3]||str[2]==str[3])
    printf("Yes");
  else if(str[0]==str[1]&&str[2]==str[3])
       printf("Yes");
  else if(str[0]==str[2]&&str[1]==str[3])
       printf("Yes");
  else  if(str[0]==str[3]&&str[1]==str[2])
       printf("Yes");
  
  
    
   else
    printf("N0");
 
}