#include <bits/stdc++.h>
using namespace std;
string s;
int a[6];
int main() {
  cin >> s;
  a[1] = s.find("Danil");
  a[2] = s.find("Olya");
  a[3] = s.find("Slava");
  a[4] = s.find("Ann");
  a[5] = s.find("Nikita");
  if (a[1] != -1 && a[2] + a[3] + a[4] + a[5] == -4) {
    s.replace(a[1], 1, "*");
    a[1] = s.find("Danil");
    if (a[1] == -1) {
      cout << "YES";
      return 0;
    }
  }
  if (a[2] != -1 && a[1] + a[3] + a[4] + a[5] == -4) {
    s.replace(a[2], 1, "*");
    a[2] = s.find("Olya");
    if (a[1] == -1) {
      cout << "YES";
      return 0;
    }
  }
  if (a[3] != -1 && a[1] + a[2] + a[4] + a[5] == -4) {
    s.replace(a[3], 1, "*");
    a[3] = s.find("Slava");
    if (a[3] == -1) {
      cout << "YES";
      return 0;
    }
  }
  if (a[4] != -1 && a[1] + a[3] + a[2] + a[5] == -4) {
    s.replace(a[4], 1, "*");
    a[4] = s.find("Ann");
    if (a[4] == -1) {
      cout << "YES";
      return 0;
    }
  }
  if (a[5] != -1 && a[1] + a[3] + a[4] + a[2] == -4) {
    s.replace(a[5], 1, "*");
    a[5] = s.find("Nikita");
    if (a[5] == -1) {
      cout << "YES";
      return 0;
    }
  }
  cout << "NO";
  return 0;
}
