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: Runtime Error)

#include<stdio.h>
#include<string.h>

int main(void){
	int i = 0;
	int cnt = 0;
  	char *s;

	scanf("%s",s);
  
  if(strcmp(&s[0],&s[1])==1){
  	cnt++;
  }
    if(strcmp(&s[0],&s[2])==1){
  	cnt++;
  }
    if(strcmp(&s[0],&s[3])==1){
  	cnt++;
  }
    if(strcmp(&s[1],&s[2])==1){
  	cnt++;
  }
    if(strcmp(&s[1],&s[3])==1){
  	cnt++;
  }
    if(strcmp(&s[2],&s[3])==1){
  	cnt++;
  }
  if(cnt == 2){
   printf("Yes");
  }else{
   printf("No");
  }
  
  return 0;

}