#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, k, count1 = 0, i, m = 0, x, y, w, p;
  string str, str1[10], str2, str3, str4;
  cin >> str;
  str1[0] = "Danil";
  str1[1] = "Olya";
  str1[2] = "Slava";
  str1[3] = "Ann";
  str1[4] = "Nikita";
  for (i = 0; i <= 4; i++) {
    size_t nPos = str.find(str1[i], 0);
    while (nPos != string::npos) {
      count1++;
      nPos = str.find(str1[i], nPos + 1);
    }
    if (count1 > 1) {
      cout << "NO";
      exit(0);
    }
  }
  if (count1 == 1)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
