#include <iostream>
using namespace std;
#include <string>
#include <vector>
#include <algorithm>
#include <map>
typedef long long ll;
#include <cmath>
#include <iomanip>

const int MOD = 1000000007;


ll POWER(ll x,ll y)
{
	ll ret=1;
	ll p=x;
	for (ll i=y;i>0;i/=2)
	{
		if (i%2) ret=(ret*p)%MOD;
		p=(p*p)%MOD;
	}
	return ret;
}
ll gcm(ll a, ll b)
{
	if (b>a) {ll c=a; a=b; b=c;}
	while (b>0)
	{
		ll r=a%b;
		a=b;
		b=r;
	}
	return a;
}


int main(int argc, char *argv[])
{
	int k,a,b;
	cin>>k>>a>>b;
	int x,y;
	x=(a+k-1)/k;
	y=b/k;

	cout<<((x<=y) ? "OK":"NG")<<endl;

	return 0;
}

