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 (Clang 3.8.0) (judge verdict: Runtime Error)

#include<stdio.h>
int main(void){
char str[4];
scanf("%s",str);

if(
(str[0]==str[1]&&str[2]==str[3]&&str[0]!=str[2])
||(str[0]==str[2]&&str[1]==str[3]&&str[0]!=str[1])
||(str[0]==str[3]&&str[1]==str[2]&&str[0]!=str[1])
)
printf("Yes");
else
printf("No");

return 0;
}