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 x[5];
    int i,o=0,t=0,j,p=0;
    scanf("%s",x);
    for(i=0;i<4;i++) {
        if(x[i]<65 || x[i]>90) p=1; ;
    }
    if(p!=1){
    for(i=1;i<4;i++)
    {
        if(x[0]==x[i]) {
         if(i<4)   j=i+1;
            else j=i-1;
            o++;
         
        }
        
    }
    if(o==1) {
        for(i=1;i<4;i++)
        {
            if(i!=j && j!=0)
            {
               if(x[j]==x[i]) t++;
            }
            
        }
    }
    if(t==1) printf("YES\n");
    else printf("NO\n");}
    else {
        printf("NO\n");
    }
    return 0;
}