include

include

include

using namespace std;

int main() {

string name;
getline (cin,name);
string d = "Danil";
string s = "Slava";
string o = "Olya";
string a = "Ann";
string n = "Nikita";
if(name == "Danil" || name == "Slava" || name == "Olya" || name == "Ann" || name == "Nikita" )
{
    cout<<"YES";
    return 0;
}
int array[10] = {-1};

array[0] = name.find(d);
if(array[0] != -1){
    name.replace(array[0], 5, "_");
}
array[1] = name.find(d);



array[2] = name.find(s);
if(array[2] != -1){
    name.replace(array[2], 5, "_");
}
array[3] = name.find(s);

array[4] = name.find(o);
if(array[4] != -1){
    name.replace(array[4], 4, "_");
}
array[5] = name.find(o);


array[6] = name.find(a);
if(array[6] != -1){
    name.replace(array[6], 3, "_");
}
array[7] = name.find(a);


array[8] = name.find(n);
if(array[8] != -1){
    name.replace(array[8], 6, "_");
}
array[9] = name.find(n);

int sum;

int y = 0;
for(int i = 0; i<10; i++)
{
    sum += array[i];
    if(array[i] != -1)
    {
       y++;
    }
}
if(sum == -10){
    cout<<"NO";
    return 0;
}
else if(y == 1 && sum!= -10)
{
    cout<<"YES";
    return 0;
}
else if(y > 1)
{
    cout<<"NO";
    return 0;
}

return 0;

}