#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
int intcmp(const void *v1, const void *v2) { return *(int *)v1 - *(int *)v2; }
inline int read() {
  int x = 0, f = 1;
  char cc = getchar();
  while (cc < '0' || cc > '9') {
    if (cc == '-') f = -1;
    cc = getchar();
  }
  while (cc >= '0' && cc <= '9') {
    x = x * 10 + cc - '0';
    cc = getchar();
  }
  return x * f;
}
string s;
string str1[] = {"Danil", "Olya", "Slava", "Ann", "Nikita"};
int main() {
  cin >> s;
  int cnt = 0;
  for (int i = 0; i < 5; i++) {
    for (int j = 0; j + str1[i].size() <= s.size(); j++) {
      string temp = s.substr(j, str1[i].size());
      if (temp == str1[i]) cnt++;
    }
  }
  if (cnt == 1)
    puts("YES");
  else
    puts("NO");
  return 0;
}
