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 s[6];
scanf("%s",s);

int i,j;char t;

for(i=0;i<3;i++)
    for(j=i+1;j<4;j++)
        if(s[i]>s[j]){
            t = s[i];
            s[i] = s[j];
            s[j] = t;
        }

if(s[0] == s[1] && s[2] == s[3])
printf("Yes\n");
else 
printf("No\n");
}