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)

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(void) {

	char input[5];
	memset(input, '\0', sizeof(input));
	int flag = 0;

	scanf("%s", input);

	for (int i = 0; i < 4; i++) {
		for (int j = 0; j < 4; j++) {
			if (input[i] == input[j]) {
				flag = 1;
				break;
			}
		}
	}

	if (flag == 1) {
		printf("Yes");
	} else{ printf("No"); }

	return 0;
}