#include<iostream>
using namespace std;
int main()
{
    int K,A,B,i;
    cin>>K>>A>>B;
    for(i=A;i<=B;i++)
    {
        if(i%K==0)
        {
            cout<<"OK";
            return 0;
        }

    }
    cout<<"NG";
    return 0;
}
