#include <bits/stdc++.h>
using namespace std;
string s;
int main() {
  int f = 0;
  cin >> s;
  int x[5] = {}, c = 2, co = 0;
  while (c--) {
    x[0] = s.find("Danil");
    if (x[0] > -1) {
      f++;
      co++;
      if (co == 2) {
        cout << "NO" << endl;
        return 0;
      }
      s[x[0] + 1] = '0';
    }
  }
  c = 2;
  co = 0;
  while (c--) {
    x[1] = s.find("Olya");
    if (x[1] > -1) {
      f++;
      co++;
      if (co == 2) {
        cout << "NO" << endl;
        return 0;
      }
      s[x[1] + 1] = '0';
    }
  }
  c = 2;
  co = 0;
  while (c--) {
    x[2] = s.find("Slava");
    if (x[2] > -1) {
      f++;
      co++;
      if (co == 2) {
        cout << "NO" << endl;
        return 0;
      }
      s[x[2] + 1] = '0';
    }
  }
  c = 2;
  co = 0;
  while (c--) {
    x[3] = s.find("Ann");
    if (x[3] > -1) {
      f++;
      co++;
      if (co == 2) {
        cout << "NO" << endl;
        return 0;
      }
      s[x[3] + 1] = '0';
    }
  }
  c = 2;
  co = 0;
  while (c--) {
    x[4] = s.find("Nikita");
    if (x[4] > -1) {
      f++;
      co++;
      if (co == 2) {
        cout << "NO" << endl;
        return 0;
      }
      s[x[4] + 1] = '0';
    }
  }
  c = 0;
  if (!f) {
    for (int i = 0; i < 5; i++) {
      if (x[i] == -1) c++;
    }
  } else
    c = 4;
  if (c == 4 && f == 1)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}
