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 juge(char *a,int c){
  int cnt1=0;
  int cnt2=0;
  for(int i=0;a[i]=='\0';i++){
    if(a[0]==a[i])
      cnt1++;
    if(a[c]==a[i])
      cnt2++;
  }
  if(cnt1 == 2 && cnt2 == 2)
    return 1;
  else 
    return 0;
}

int main(){
  char a[5];
  int c;
  scanf("%s",a);

  for(c=0;a[c]!='\0' && a[0]==a[c];c++);
  
  if(c==5)
    printf("No");
  else 
    if(juge(a,c))
      printf("Yes");
    else 
      printf("No");
   
  return 0;
}