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()
{
    char ch[4];

    scanf("%[^\n]",ch);

    if(ch[0]==ch[1]&&ch[2]==ch[3]&&ch[0]!=ch[2]||
            ch[0]==ch[3]&&ch[1]==ch[2]&&ch[0]!=ch[1]||
            ch[0]==ch[2]&&ch[1]==ch[3]&&ch[0]!=ch[1])
    {
        printf("Yes\nS consists of A and S which both appear twice in S.");
    }
    else
    {
        printf("No\n");
    }

    return 0;
}