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)

using namespace std;
#include<iostream>

#define rep(i, n) for (int i = 0; i < n; i++)

int main(){
    string S;
    cin >> S;
    if(S[1]==S[2]){
        if(S[3]==S[4]){
            cout << "Yes";
            return 0;
        }
    }
    if(S[1]==S[3]){
        if(S[2]==S[4]){
            cout << "Yes";
            return 0;
        }
    }
    if(S[1]==S[4]){
        if(S[2]==S[3]){
            cout << "Yes";
            return 0;
        }
    }
    if(S[2]==S[3]){
        if(S[1]==S[4]){
            cout << "Yes";
            return 0;
        }
    }
    if(S[2]==S[4]){
        if(S[1]==S[3]){
            cout << "Yes";
            return 0;
        }
    }
    if(S[3]==S[4]){
        if(S[1]==S[2]){
            cout << "Yes";
            return 0;
        }
    }
    cout << "No";
    return 0;
}