#include <bits/stdc++.h>
using namespace std;
int main() {
  long long t, i, j, k, l, p, a, b, n, ans = 0, ans1 = 0;
  string A;
  cin >> A;
  l = A.size();
  if (l < 4) {
    cout << "No\n";
    return 0;
  }
  int B[50] = {0};
  sort(A.begin(), A.end());
  char c = A[0];
  for (i = 1; i < l; i++) {
    if (c != A[i]) {
      ans++;
    }
    c = A[i];
  }
  for (i = 0; i < l; i++) {
    B[A[i] - 97]++;
  }
  ans++;
  for (i = 0; i <= 27; i++) {
    if (B[i] >= 2) ans1++;
  }
  if (ans > 4) {
    cout << "No\n";
    return 0;
  }
  if (ans < 2)
    cout << "No\n";
  else if (ans >= 3)
    cout << "Yes\n";
  else if (ans == 2 && ans1 == 1)
    cout << "No\n";
  else {
    cout << "Yes\n";
  }
}
