#include <bits/stdc++.h>
using namespace std;
int main() {
  string str;
  cin >> str;
  cin.ignore();
  int count1 = 0;
  size_t nPos = str.find("Danil", 0);
  while (nPos != string::npos) {
    count1++;
    nPos = str.find("Danil", nPos + 1);
  }
  int count2 = 0;
  size_t nPos1 = str.find("Olya", 0);
  while (nPos1 != string::npos) {
    count2++;
    nPos1 = str.find("Olya", nPos1 + 1);
  }
  int count3 = 0;
  size_t nPos2 = str.find("Slava", 0);
  while (nPos2 != string::npos) {
    count3++;
    nPos2 = str.find("Slava", nPos2 + 1);
  }
  int count4 = 0;
  size_t nPos3 = str.find("Ann", 0);
  while (nPos3 != string::npos) {
    count4++;
    nPos3 = str.find("Ann", nPos3 + 1);
  }
  int count5 = 0;
  size_t nPos4 = str.find("Nikita", 0);
  while (nPos4 != string::npos) {
    count5++;
    nPos4 = str.find("Nikita", nPos4 + 1);
  }
  if (count5 + count4 + count3 + count2 + count1 == 1) {
    cout << "YES";
  } else
    cout << "NO";
}
