"""
 *
 * Author:  <NAME>(coderemite)
 * Email: <EMAIL>
 *
 """
v=["Danil","Olya","Slava","Ann","Nikita"]
a=input()
print('YNEOS'[sum(a.count(x)for x in v)!=1::2])

"""
 *
 * Author:  <NAME>(coderemite)
 * Email: <EMAIL>
 *
 """
v=["Danil","Olya","Slava","Ann","Nikita"]
a=input()
print('YNEOS'[sum(a.count(x)for x in v)!=1::2])

*  * Author:  <NAME>(coderemite)  * Email: <EMAIL>  *