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>
#include <stdlib.h>
int compare(const void *a,const void *b){
    if(*(int *)a>*(int *)b)return 1;
    return -1;
}
int main()
{   char s[5];
    scanf("%s",s);
    int a[4];
    a[0]=s[0]-'A';
    a[1]=s[1]-'A';
    a[2]=s[2]-'A';
    a[3]=s[3]-'A';
    qsort(a,4,sizeof(int),compare);
    if(a[0]==a[1]&&a[2]==a[3]&&a[1]!=a[2])
    printf("Yes");
    else printf("No");

    return 0;
}