#include <bits/stdc++.h>
using namespace std;
const long long int sz = 1e5 + 5;
const long long int szz = 1e6 + 6;
const long long int mod = 1e9 + 7;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(nullptr);
  cout.tie(nullptr);
  clock_t startTime = clock();
  string s;
  cin >> s;
  if (s.size() < 4) {
    cout << "No";
    return 0;
  }
  map<char, long long int> mp;
  for (auto x : s) {
    mp[x]++;
  }
  if (mp.size() > 4 or mp.size() == 1) {
    cout << "No\n";
    return 0;
  } else if (mp.size() == 4 or mp.size() == 3) {
    cout << "Yes\n";
    return 0;
  } else if (mp.size() == 2) {
    long long int mini = 1e13;
    for (auto x : mp) {
      if (x.second < 2) {
        cout << "No\n";
        return 0;
      }
    }
    cout << "Yes\n";
    return 0;
  }
  cerr << "\n"
       << setprecision(20)
       << double(clock() - startTime) / (double)CLOCKS_PER_SEC << " seconds."
       << "\n";
}
