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()
{
    char a[4];
    int p=0;
    scanf("%s%s%s%s",&a[1],&a[2],&a[3],&a[4]);
    if(a[1]==a[2]){
        p+=1;
    }
    if(a[1]==a[3]){
        p+=1;
    }
    if(a[1]==a[4]){
        p+=1;
    }
    if(a[2]==a[3]){
        p+=1;
    }
    if(a[2]==a[4]){
        p+=1;
    }
    if(a[3]==a[4]){
        p+=1;
    }
if(p==2){
    printf("Yes");
}else{
    printf("No");
}
}