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<string.h>
int main()
{
    char x[5];
    int j,i,c=0;
    gets(x);
    for(i=1;i<4;i++)
    {
        if(x[0] == x[i]) j=i;
    }
    for(i=1;i<4;i++)
    {
        if(x[j]!=x[i] && x[0]!=x[i])
        c++;
    }

    if(c==2 ) printf("Yes\n");
    else printf("No\n");
    return 0;
}