#include <bits/stdc++.h>
using namespace std;

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  string s;
  getline(cin, s);
  int n = s.size();
  for (int r = 1; r <= n; ++r) {
    for (int l = 0; l < r; ++l) {
      if (r - l < 2) {
        continue;
      }
      vector<bool> b(n);
      for (int i = l; i < r; i += 2) {
        b[i] = true;
      }
      string x, y;
      for (int i = 0; i < n; ++i) {
        if (b[i]) {
          x += s[i];
        } else {
          y += s[i];
        }
      }
      sort(begin(x), end(x));
      sort(begin(y), end(y));
      if (x.find(' ') != string::npos) {
        continue;
      }
      string z;
      set_intersection(begin(x), end(x), begin(y), end(y), back_inserter(z));
      if (z.empty()) {
        cout << "Yes\n";
        exit(0);
      }
    }
  }
  cout << "NO\n";
}