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 (Clang 3.8.0) (judge verdict: Accepted)

// #include<bits/stdc++.h>
#include<iostream>
#include<string>
//マップ使う
using namespace std;
int main(){
    string s;
    char a,b;
    int q=0;
    cin >> s;
    const char* x= s.c_str();

    for(int i=0; i<3; i++){
        for(int j=i+1; j<4; j++){
            if(x[i]==x[j]) q++;
        }
    }
    if(q==2) cout<< "Yes" << endl;
    else cout << "No" << endl;
}