#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const long long LINF = 0x3f3f3f3f3f3f3f3f;
const int N = 1e2 + 7;
string s;
int main() {
  cin >> s;
  int cnt = 0;
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == 'D') {
      if (s.substr(i, 5) == "Danil") cnt++;
    } else if (s[i] == 'O') {
      if (s.substr(i, 4) == "Olya") cnt++;
    } else if (s[i] == 'S') {
      if (s.substr(i, 5) == "Slava") cnt++;
    } else if (s[i] == 'A') {
      if (s.substr(i, 3) == "Ann") cnt++;
    } else if (s[i] == 'N') {
      if (s.substr(i, 6) == "Nikita") cnt++;
    }
  }
  printf("%s\n", cnt == 1 ? "YES" : "NO");
  return 0;
}
