#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void solve() {
  ll n;
  string second;
  cin >> second;
  n = second.size();
  map<string, ll> a;
  a["Danil"] = 1;
  a["Olya"] = 1;
  a["Slava"] = 1;
  a["Ann"] = 1;
  a["Nikita"] = 1;
  for (ll i = 0; i < n; i++) {
    if (second[i] == 'D' && (n - i) >= 5) {
      if (a[second.substr(i, 5)] > 0) a["Danil"]++;
    } else if (second[i] == 'O' && (n - i) >= 4) {
      if (a[second.substr(i, 4)] > 0) a["Olya"]++;
    } else if (second[i] == 'S' && (n - i) >= 5) {
      if (a[second.substr(i, 5)] > 0) a["Slava"]++;
    } else if (second[i] == 'A' && (n - i) >= 3) {
      if (a[second.substr(i, 3)] > 0) a["Ann"]++;
    } else if (second[i] == 'N' && (n - i) >= 6) {
      if (a[second.substr(i, 6)] > 0) a["Nikita"]++;
    }
  }
  a["Danil"]--;
  a["Olya"]--;
  a["Slava"]--;
  a["Ann"]--;
  a["Nikita"]--;
  ll sum = a["Danil"] + a["Olya"] + a["Slava"] + a["Ann"] + a["Nikita"];
  if (sum != 1) {
    cout << "NO";
  } else {
    cout << "YES";
  }
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  solve();
  return 0;
}
