#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  string str;
  cin >> str;
  set<char> s;
  map<char, int> mp;
  set<int> nC;
  for (auto it : str) s.insert(it), mp[it]++;
  for (auto it : mp) nC.insert(it.second);
  int disC = s.size();
  int f = 1;
  if (str.size() < 4)
    f = 0;
  else if (disC > 4)
    f = 0;
  else if (disC == 2 && nC.find(1) != nC.end())
    f = 0;
  else if (disC == 1)
    f = 0;
  if (f)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
  return 0;
}
