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++14 (Clang 3.8.0) (judge verdict: Accepted)

#include<stdio.h>
int main(){
	char a[8],c;
	scanf("%s",a);
	for(int i=0;i<3;i++)
	for(int j=0;j<3-i;j++)
	if(a[j]<a[j+1])
	{
	c=a[j];
	a[j]=a[j+1];
	a[j+1]=c;
    }
if(a[0]==a[1]&&a[2]==a[3]&&a[0]!=a[2]&&a[0]!=a[3])
	printf("Yes\n");
	else
	printf("No\n");
	return 0;
}