#include <bits/stdc++.h>
using namespace std;
int one(string s) {
  int count = 0;
  size_t nPos = s.find("Danil");
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Danil", nPos + 1);
  }
  return count;
}
int two(string s) {
  int count = 0;
  size_t nPos = s.find("Olya");
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Olya", nPos + 1);
  }
  return count;
}
int three(string s) {
  int count = 0;
  size_t nPos = s.find("Slava");
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Slava", nPos + 1);
  }
  return count;
}
int four(string s) {
  int count = 0;
  size_t nPos = s.find("Ann");
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Ann", nPos + 1);
  }
  return count;
}
int five(string s) {
  int count = 0;
  size_t nPos = s.find("Nikita");
  while (nPos != string::npos) {
    count++;
    nPos = s.find("Nikita", nPos + 1);
  }
  return count;
}
int main() {
  string s;
  cin >> s;
  int one1 = one(s), two1 = two(s), three1 = three(s), four1 = four(s),
      five1 = five(s);
  if ((one1 == 1 && !two1 && !three1 && !four1 && !five1) ||
      (!one1 && two1 == 1 && !three1 && !four1 && !five1) ||
      (!one1 && !two1 == 1 && three1 && !four1 && !five1) ||
      (!one1 && !two1 && !three1 && four1 == 1 && !five1) ||
      (!one1 && !two1 && !three1 && !four1 && five1 == 1)) {
    cout << "YES" << endl;
  } else {
    cout << "NO" << endl;
  }
  return 0;
}
