#include <bits/stdc++.h>
#define ll long long int
#define endl "\n"
using namespace std;
#define M 1000000007
#define pb push_back
#define rep(i, a, b) for(int i = a; i <= b; i++)
ll mod = 998244353;


int main()
{
	ios_base::sync_with_stdio(false);
    cin.tie(NULL);
	int t; t = 1;
	//cin >> t;
	while(t--)
	{	
		ll k, a, b;
		cin >> k >> a >> b;
		if(a%k == 0 || b%k == 0)
			cout << "OK" << endl;
		else if(abs(a-b) >= k)
			cout << "OK" << endl;
		else
			cout << "NG" << endl;
	}
		
}  