#include <bits/stdc++.h>
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define ll long long int
#define endl "\n"
#define f(i, a, b) for(ll i=a; i<b; i++)
#define fb(i, a, b) for(ll i=a; i>=b; i--)
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define vi vector <int>
#define vl vector <long long>
#define pi pair <int, int>
#define sz(x) (int) x.size()
#define M 100005
#define mod 1000000007
using namespace std;

void solve()
{
	int k, a, b;
	cin>>k>>a>>b;
	if(b-a >= k || a%k >= b%k || a%k == 0 || b %k == 0) cout<<"OK\n";
	else cout<<"NG\n";
}

int main()
{
    IOS
    int t = 1;
    //cin>>t;
    f(tno, 1, t+1)
    {
        solve();
    }
    return 0;
}