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: Accepted)

#include <stdio.h>
int main(void){
    // Your code here!
    char n[8];
    scanf("%s",n);
   int lsee=0;
   
    int i,j;
   
    for(i=0;i<4;i++){
        for (j=0;j<4;j++){
        
            if(n[i]==n[j]){
                lsee++;
                
            }
            //printf("%d\n",lsee);
           
            
        }
        
        
    }
    if(lsee==8){
        printf("Yes\n");
    }else{
        printf("No\n");
    }
    return (0);
}