#include <bits/stdc++.h>
using namespace std;
int main() {
  string d[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
  int ls, ld, i, l, j, k, m, cnt = 0;
  string s;
  cin >> s;
  for (j = 0; j < 5; j++) {
    ld = d[j].size();
    for (i = 0; i < s.size(); i = m) {
      l = 0;
      m = i;
      for (k = 0; k < ld; k++) {
        if (s[m] == d[j][k]) {
          l++;
          m++;
        }
      }
      if (m == i) m++;
      if (l == ld) cnt++;
    }
  }
  if (cnt == 1)
    printf("YES\n");
  else
    printf("NO\n");
  return 0;
}
