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 a[10];
    char s[10];
    int ans =0;

    scanf("%s", &s);

    for(int i=0; i<4; i++){
        for(int j=i+1; j<4; j++){
            if(s[i] == s[j]){
                ans +=1;
            }
        }
    }
    if(ans == 2){
        printf("Yes");
    }else{
        printf("No");
    }


    return 0;
}