#include<bits/stdc++.h>

using namespace std;

#define read(in) freopen("Input.txt","r",stdin)
#define write(out) freopen("Ouput.txt","w",stdout)
#define Pi 2*acos(0.0)

typedef long long int lli;

lli i,j,k,l,m,n,t,a,b,c,d,x,y,p,q,s,r,f,sum=0,total=0;

int main()
{
    ios_base :: sync_with_stdio(false);
    cin.tie(0);

    //read(in);

    cin>>k>>a>>b;
    sum=0;
    for(i=a ; i<=b ; i++)
    {
    	if(i%k==0)
    	{
    		sum=1;break;
    	}
    }
    if(sum==1)	cout<<"OK\n";
    else cout<<"NG\n";
}