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 a[4]; scanf("%s",a);
  if(a[0]==a[1]){
    if(a[2]==a[3] && a[0]!=a[2]) printf("Yes\n");
    else printf("No\n");
  }else if(a[0]==a[2]){
    if(a[1]==a[3] && a[1]!=a[2]) printf("Yes\n");
    else printf("No\n");
  }else if(a[0]==a[3]){
    if(a[2]==a[1] && a[0]!=a[2]) printf("Yes\n");
    else printf("No\n");
  }
    
  
  /*int n,a,b; scanf("%d%d%d",&n,&a,&b);
  if(n*a<b) printf("%d\n",n*a);
  else printf("%d\n",b);*/
  return 0;
}