#include <bits/stdc++.h>
using namespace std;
int main() {
  char s[110];
  while (scanf("%s", s) != EOF) {
    int len = strlen(s);
    int i, j;
    int ans = 0;
    for (i = 0; i < len; i++) {
      char str[110];
      if (s[i] == 'A') {
        for (j = 0; j < 3; j++) {
          str[j] = s[i + j];
        }
        str[j] = '\0';
        if (strcmp(str, "Ann") == 0) {
          ans++;
        }
        continue;
      }
      if (s[i] == 'D') {
        for (j = 0; j < 5; j++) {
          str[j] = s[i + j];
        }
        str[j] = '\0';
        if (strcmp(str, "Danil") == 0) {
          ans++;
        }
        continue;
      }
      if (s[i] == 'O') {
        for (j = 0; j < 4; j++) {
          str[j] = s[i + j];
        }
        str[j] = '\0';
        if (strcmp(str, "Olya") == 0) {
          ans++;
        }
        continue;
      }
      if (s[i] == 'S') {
        for (j = 0; j < 5; j++) {
          str[j] = s[i + j];
        }
        str[j] = '\0';
        if (strcmp(str, "Slava") == 0) {
          ans++;
        }
        continue;
      }
      if (s[i] == 'N') {
        for (j = 0; j < 6; j++) {
          str[j] = s[i + j];
        }
        str[j] = '\0';
        if (strcmp(str, "Nikita") == 0) {
          ans++;
        }
        continue;
      }
    }
    if (ans == 1)
      printf("YES\n");
    else
      printf("NO\n");
  }
  return 0;
}
