#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1.0);
const int INF = 0x3f3f3f3f;
const int N = 2e5 + 7;
int main() {
  string s;
  cin >> s;
  int len = s.length();
  map<char, int> m;
  map<char, int>::iterator it;
  int z = 0;
  for (int i = 0; i < len; ++i) {
    if (m[s[i]] == 0) {
      z++;
      m[s[i]] = 1;
    } else {
      m[s[i]] += 1;
    }
  }
  if (z == 4) {
    cout << "Yes" << endl;
  } else if (z == 3) {
    int flag = false;
    it = m.begin();
    while (it != m.end()) {
      if (it->second >= 2) {
        flag = true;
        break;
      }
      it++;
    }
    if (flag)
      cout << "Yes" << endl;
    else
      cout << "No" << endl;
  } else if (z == 2) {
    int flag = true;
    it = m.begin();
    while (it != m.end()) {
      if (it->second < 2) {
        flag = false;
        break;
      }
      it++;
    }
    if (flag)
      cout << "Yes" << endl;
    else
      cout << "No" << endl;
  } else {
    cout << "No" << endl;
  }
}
