#include <bits/stdc++.h>
using namespace std;
const long long MAXN = 5e6 + 5;
const long long MOD = 1e9 + 7;
const long double eps = 1e-6;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  map<char, int> cnt;
  for (int i = 0; i < s.size(); ++i) {
    cnt[s[i]]++;
  }
  if (cnt.size() == 2) {
    for (auto it = begin(cnt); it != end(cnt); it++) {
      if (it->second == 1) {
        cout << "No\n";
        return 0;
      }
    }
    cout << "Yes\n";
    return 0;
  }
  if (cnt.size() == 3) {
    if (s.size() == 3) {
      cout << "No\n";
      return 0;
    } else {
      cout << "Yes\n";
      return 0;
    }
  }
  if (cnt.size() == 4) {
    cout << "Yes\n";
    return 0;
  }
  cout << "No\n";
  return 0;
}
