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 Java8 (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.util.Scanner;

public class Main {
  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    int[] p = new int[sc.nextInt()];

    for(int pIdx=0;pIdx<p.length;pIdx++){
      p[pIdx]=sc.nextInt();
    }

    int count=0;
    for(int pIdx = 1;pIdx<p.length-1;pIdx++){
      if(isMatch(p[pIdx-1],p[pIdx],p[pIdx+1]))count++;
    }
    System.out.println(count);
  }

  static boolean isMatch(int pm1, int p0, int pp1) {
    return (!(p0 < pm1 && p0 < pp1)) && !(p0 > pm1 && p0 > pp1);
  }
}