#include <bits/stdc++.h>
using namespace std;
int main(){
	string s; cin >> s;
	sort(s.begin(), s.end());
	if(s[0] == s[1] && s[2] == s[3] && s[1] != s[2]) cout << "Yes" << endl;
	else cout << "No" << endl;
	return 0;
}
