#include <iostream>
#include <bits/stdc++.h> 
using namespace std;

int main()
{
   int a,b,k;
   cin>>k;
   cin>>a>>b;
   for(int i=a;i<=b;i++)
   {
       if(i%k==0)
      {  cout<<"OK";
        return 0;
      }
    
   }
   cout<<"NG";
   return 0;
}