#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <map>
#include <set>
#include <queue>
#include <iomanip>
#include <cstring>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i,n) for (int i = 0; i < int(n);i++)

int main(){
  string s;
  cin >> s;
  sort(s.begin(),s.end());
  s.erase(unique(s.begin(),s.end()),s.end());
  if (s.size() == 2) cout << "Yes\n";
  else cout << "No\n";
  
  return 0;
}