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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<string.h>
int main()
{
   char S[20];
   int C;
   scanf("%s",S);
   if(S[0]==S[1] || S[0]==S[2] || S[0]==S[3] || S[1]==S[2] || S[1]==S[3] || S[2]==S[3]) ++C;
   if(S[2]==S[3] || S[1]==S[3] || S[1]==S[2] || S[0]==S[3] || S[0]==S[2] || S[0]==S[1]) ++C;
   if(C=2)
   {
       printf ("YES");
   }
   else
    printf("No");
   return 0;
}