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(void){
  int i,n,count=0;
  scanf("%d\n",&n);
  int p[n];
  for(i=0;i<n;i++){
    scanf("%d",&p[i]);
  }

  for(i=0;i<n-1;i++){
    if((p[i]<p[i+1])&&(p[i+1]<p[i+2])){
      count+=1;
    }
    else if((p[i]>p[i+1])&&(p[i+1]>p[i+2])){
      count+=1;
    }
  }

  printf("%d\n",count);

  return 0;
}