#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  long l = s.length(), i;
  long hash[26] = {0};
  for (i = 0; i < l; i++) {
    hash[s[i] - 'a']++;
  }
  long count = 0;
  for (i = 0; i < 26; i++) {
    if (hash[i] > 0) count++;
  }
  if (count >= 5 || count == 1)
    cout << "No\n";
  else if (count == 2) {
    long c1 = 0, c2 = 0;
    for (i = 0; i < 26; i++) {
      if (hash[i] > 0) {
        if (!c1)
          c1 = hash[i];
        else if (!c2)
          c2 = hash[i];
      }
    }
    if (c1 > 1 && c2 > 1)
      cout << "Yes";
    else
      cout << "No";
  } else if (count == 3) {
    if (l >= 4)
      cout << "Yes";
    else
      cout << "No";
  } else if (count == 4)
    cout << "Yes";
}
