#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";
	}
	else cout<<"No";
  return 0;
}
