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(){
    int c,d,e,f;
    c = getchar();
    d = getchar();
    e = getchar();
    f = getchar();
    if((c==d)&&(d==e)&&(e==f)){
        printf("No\n");
    }
    else if((c==d)&&(e==f) ){
        printf("Yes\n");
    }
    else if((c==e)&&(d==f)){
        printf("Yes\n");
    }
    else if((c==f)&&(d==e)){
        printf("Yes\n");
    }
    
    else{
        printf("No\n");
    }
}