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(){
	char s[4];
	int i;
	char tmp[4];
	int j=0;
	scanf("%s",s);
	static int cnt[4];
	int k;
	int l=0;
	for(i=0;i<4;i++){
		tmp[j]=s[i];
		for(k=i+1;k<4-i;k++){
			if(tmp[j]==s[k])cnt[l]++;
		}
		if(cnt[l]!=0)l++;
	}
	if(cnt[0]*cnt[1] == 1)printf("Yes\n");
	else printf("No\n");

 return 0;
}