#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, k = 0, t, l, n, m, c = 0, flag = 1, last;
  string ch;
  cin >> ch;
  char c1, c2, c3, c4;
  map<char, int> mp;
  l = ch.length();
  for (i = 0; i < l; i++) {
    if (mp[ch[i]] == 0) {
      c++;
      if (c == 1) c1 = ch[i];
      if (c == 2) c2 = ch[i];
      if (c == 3) c3 = ch[i];
      if (c == 4) c4 = ch[i];
    }
    mp[ch[i]]++;
  }
  if (c > 4) {
    cout << "No";
    return 0;
  } else if (l <= 3) {
    cout << "No";
    return 0;
  } else if (c == 1) {
    cout << "No";
    return 0;
  } else if (c == 2) {
    if (mp[c1] == 1 || mp[c2] == 1) {
      cout << "No";
      return 0;
    }
  }
  if (!flag)
    cout << "No";
  else
    cout << "Yes";
  return 0;
}
