#include <bits/stdc++.h>
using namespace std;
int main() {
  char str[11000];
  long long i, j, k, len1, len2, fl = 0, flag = 0, flg;
  cin >> str;
  len1 = strlen(str);
  string search[6];
  search[0] = "Danil";
  search[1] = "Olya";
  search[2] = "Slava";
  search[3] = "Ann";
  search[4] = "Nikita";
  for (k = 0; k < 5; k++) {
    flag = 0;
    len2 = search[k].length();
    flg = 0;
    for (i = 0; i <= len1 - len2; i++) {
      for (j = i; j < i + len2; j++) {
        flag = 1;
        if (str[j] != search[k][j - i]) {
          flag = 0;
          break;
        }
      }
      if (flag == 1) {
        fl++;
      }
    }
  }
  if (fl != 1) {
    cout << "NO\n";
  } else
    cout << "YES\n";
  return 0;
}
