#include <bits/stdc++.h>
using namespace std;
struct FastIO {
  static const int S = 1310720;
  int wpos;
  char wbuf[S];
  FastIO() : wpos(0) {}
  inline int xchar() {
    static char buf[S];
    static int len = 0, pos = 0;
    if (pos == len) pos = 0, len = fread(buf, 1, S, stdin);
    if (pos == len) return -1;
    return buf[pos++];
  }
  inline int xuint() {
    int c = xchar(), x = 0;
    while (c <= 32) c = xchar();
    for (; '0' <= c && c <= '9'; c = xchar()) x = x * 10 + c - '0';
    return x;
  }
  inline int xint() {
    int s = 1, c = xchar(), x = 0;
    while (c <= 32) c = xchar();
    if (c == '-') s = -1, c = xchar();
    for (; '0' <= c && c <= '9'; c = xchar()) x = x * 10 + c - '0';
    return x * s;
  }
  inline long long xlongint() {
    long long s = 1, c = xchar(), x = 0;
    while (c <= 32) c = xchar();
    if (c == '-') s = -1, c = xchar();
    for (; '0' <= c && c <= '9'; c = xchar()) x = x * 10 + c - '0';
    return x * s;
  }
  inline void xstring(char *s) {
    int c = xchar();
    while (c <= 32) c = xchar();
    for (; c > 32; c = xchar()) *s++ = c;
    *s = 0;
  }
  inline void wchar(int x) {
    if (wpos == S) fwrite(wbuf, 1, S, stdout), wpos = 0;
    wbuf[wpos++] = x;
  }
  inline void wint(long long x) {
    if (x < 0) wchar('-'), x = -x;
    char s[24];
    int n = 0;
    while (x || !n) s[n++] = '0' + x % 10, x /= 10;
    while (n--) wchar(s[n]);
  }
  inline void wstring(const char *s) {
    while (*s) wchar(*s++);
  }
  ~FastIO() {
    if (wpos) fwrite(wbuf, 1, wpos, stdout), wpos = 0;
  }
} io;
const int maxn = 5;
string strs[5] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
int main(int argc, char const *argv[]) {
  ios::sync_with_stdio(0);
  cin.tie(0);
  string str;
  while (cin >> str) {
    int cnt = 0;
    int len = str.length();
    for (int i = 0; i < maxn; ++i) {
      string tmp = str;
      while ((int)tmp.find(strs[i]) != -1) {
        ++cnt;
        tmp = tmp.substr((int)tmp.find(strs[i]) + 1);
      }
    }
    if (cnt == 1)
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  }
  return 0;
}
