#include <bits/stdc++.h>
using namespace std;
void showvec1d(vector<int> v) {
  int n = v.size();
  cout << "-------------start1dv--------------------"
       << "\n";
  for (int i = 0; i < n; i++) cout << v[i] << " ";
  cout << "\n";
  cout << "--------------end1dv-------------------"
       << "\n";
}
void showvec2d(vector<vector<int> > v) {
  int n = v.size();
  cout << "--------------start2dv-----------------------\n";
  for (int i = 0; i < n; i++) {
    int sz = v[i].size();
    for (int j = 0; j < sz; j++) cout << v[i][j] << " ";
    cout << "\n";
  }
  cout << "-------------end2dv------------------"
       << "\n";
}
void solve() {
  string s;
  cin >> s;
  int count = 0;
  size_t nPos = s.find("Danil", 0);
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Danil", nPos + 1);
  }
  nPos = s.find("Olya", 0);
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Olya", nPos + 1);
  }
  nPos = s.find("Slava", 0);
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Slava", nPos + 1);
  }
  nPos = s.find("Ann", 0);
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Ann", nPos + 1);
  }
  nPos = s.find("Nikita", 0);
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Nikita", nPos + 1);
  }
  if (count == 1)
    cout << "YES"
         << "\n";
  else
    cout << "NO"
         << "\n";
}
int main() {
  cin.tie(0);
  cout.tie(0);
  cin.sync_with_stdio(0);
  cout.sync_with_stdio(0);
  int TC = 1;
  for (int ZZ = 1; ZZ <= TC; ZZ++) {
    clock_t start = clock();
    solve();
    clock_t end = clock();
    cerr << "Time: " << (double)(end - start) / CLOCKS_PER_SEC << " seconds"
         << '\n';
  }
  return 0;
}
