#include <bits/stdc++.h>
using namespace std;
inline void read(int &x) {
  register int c = getchar();
  x = 0;
  int neg = 0;
  for (; ((c < 48 || c > 57) && c != '-'); c = getchar())
    ;
  if (c == '-') {
    neg = 1;
    c = getchar();
  }
  for (; c > 47 && c < 58; c = getchar()) {
    x = (x << 1) + (x << 3) + c - 48;
  }
  if (neg) x = -x;
}
inline void writeln(int x) {
  char buffor[21];
  register int i = 0;
  int neg = 0;
  if (x < 0) {
    neg = 1;
    x = -x;
  }
  do {
    buffor[i++] = (x % 10) + '0';
    x /= 10;
  } while (x);
  i--;
  if (neg) putchar('-');
  while (i >= 0) putchar(buffor[i--]);
  putchar('\n');
}
string s;
int n;
int res = 0;
bool check(int l, int r) {
  if (l + r - 1 >= n) return false;
  string p = s.substr(l, r);
  if (p == "Danil" or p == "Olya" or p == "Slava" or p == "Ann" or
      p == "Nikita")
    return true;
  return false;
}
void input() {
  cin >> s;
  n = s.size();
  for (int i = 0; i <= n - 1; i++) {
    if (check(i, 3)) res++;
    if (check(i, 4)) res++;
    if (check(i, 5)) res++;
    if (check(i, 6)) res++;
  }
  if (res == 1)
    cout << "YES";
  else
    cout << "NO";
}
void solve() {}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  input();
  solve();
  return 0;
}
