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 <bits/stdc++.h>
using namespace std;

int main(){
    string s;
    cin >> s;
    
    map<int ,char> m;
    
    for(auto x:  s){
        if(m.find(x)==m.end()){
            m[x]=0;
        }else{
            m[x]++;
        }
    }
    int c = 0;
    for(auto i = m.begin(); i != m.end(); ++i){
        c = max(i->first,c);
    }
    cout << c;
    return 0;
}