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>
#define _GLIBCXX_DEBUG
#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)
#define gnr(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define per(i,b) gnr(i,0,b)
#define bg begin()
#define ed end()
#define rbg rbegin()
#define red rend()
#define all(x) x.bg,x.ed
#define rall(x) x.rbg,x.red
#define pb push_back
#define pf push_front
#define eb emplace_back
using namespace std;
typedef long long ll;
template<class t,class u> bool chmax(t&a,u b){if(a<b){a=b; return true;} return false;}
template<class t,class u> bool chmin(t&a,u b){if(a>b){a=b; return true;} return false;}
template<class t,class u> t MAX(t a,u b){if(a>=b) return a; return b;}
template<class t,class u> t MIN(t a,u b){if(a<=b) return a; return b;}
template<class t> int SIZE(t s){return (int)s.size();}
template<class t> using vc=vector<t>;
template<class t> using vvc=vc<vc<t>>;
using vvi=vc<vc<int>>;
using pi=pair<int,int>;
using vi=vc<int>;
void yes(){ cout << "Yes" << endl; }
void no(){ cout << "No" << endl; }
const long long INF = 1LL << 60;

int main(){
    cout << fixed << setprecision(20);
    string s; cin >> s;
    if(s[0] == s[1] && s[2] == s[3]) yes();
    else if(s[0] ==s[2] && s[1] == s[3]) yes();
    else if(s[0] ==s[3] && s[1]==s[2]) yes();
    else no();
    return 0;
}