#include <iostream>
using namespace std;
int main(){
int a;
cin>>a;
if(25<=a&&a<=30){
cout<<"ok!";
}
else{
cout<<"no!";
}
return 0;
}
#include <iostream>
using namespace std;
int main(){
int a;
cin>>a;
if(25<=a&&a<=30){
cout<<"ok!";
}
else{
cout<<"no!";
}
return 0;
}