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, j;
	char str[5];
	int sum = 0;
	scanf("%s", str);



	for (i = 0; i < 4; i++) {
		sum += str[i];
	}

	if(str[0]+str[1]==sum/2||str[0]+str[2]==sum/2||str[0]+str[3]==sum/2){
		printf("Yes\n");
}
else printf("No\n"); 

	printf("%s", str);
	printf("%d\n", sum);
	printf("%d %d %d", str[0],str[1],sum/2);

	
	return 0;
}