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