#include<bits/stdc++.h>
using namespace std;
int main()
{
    int k,a,b;
    cin>>k>>a>>b;
   if(a%k==0||b%k==0)
   {
       cout<<"OK"<<endl;
   }
   else
   {
       int m=a/k;
       if((m+1)*k>b)
        cout<<"NG"<<endl;
       else
        cout<<"OK"<<endl;
   }

}