#include <bits/stdc++.h>
using namespace std;
char s[205];
string b[6];
int a[6];
void check(int x) {
  for (int i = 1; i <= 5; i++) {
    bool f = 1;
    for (int j = 0; j < b[i].length(); j++) {
      if (s[j + x] != b[i][j]) {
        f = 0;
        break;
      }
    }
    if (f) a[i]++;
  }
}
void solve() {
  scanf("%s", s);
  b[1] = "Danil";
  b[2] = "Olya";
  b[3] = "Slava";
  b[4] = "Ann";
  b[5] = "Nikita";
  int len = strlen(s);
  int ans = 0;
  for (int i = 0; i < len; i++) {
    check(i);
  }
  for (int i = 1; i <= 5; i++) {
    ans += a[i];
  }
  cout << endl;
  printf("%s", ans == 1 ? "YES" : "NO");
  return;
}
int main() {
  solve();
  return 0;
}
