#include <bits/stdc++.h>
using namespace std;
const int inf = 1 << 30;
const long long INF = 1ll << 60;
const double Inf = 1e20;
const double eps = 1e-9;
void gmax(int &a, int b) { a = (a > b ? a : b); }
void gmin(int &a, int b) { a = (a < b ? a : b); }
const int maxn = 105;
const char b[7][maxn] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
char a[maxn];
int n;
int _cnt(int id) {
  int l1 = strlen(b[id]), ans = 0;
  for (int i = 0; i <= n - l1; ++i) {
    for (int j = 0; j <= l1 - 1; ++j)
      if (b[id][j] != a[i + j]) goto failed;
    ++ans;
  failed:;
  }
  return ans;
}
int main() {
  gets(a);
  n = strlen(a);
  int sum = 0;
  for (int i = 0; i <= 4; ++i) sum += _cnt(i);
  if (sum != 1)
    printf("NO");
  else
    printf("YES");
  return 0;
}
