
// Problem : A - We Love Golf
// Contest : AtCoder - AtCoder Beginner Contest 165
// URL : https://atcoder.jp/contests/abc165/tasks/abc165_a
// Memory Limit : 1024 MB
// Time Limit : 2000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

#include <bits/stdc++.h>

#define FIO ios_base::sync_with_stdio(0); cin.tie(0);
#define T() int tt; cin >> tt; rep1(qq,1,tt)
#define rep(i,start,lim) for(int i=start;i<lim;i++)
#define rep1(i,start,lim) for(int i=start; i<=lim; ++i)
#define repd(i,start,lim) for(int i=start;i>=lim;i--)
#define mp make_pair
#define pb push_back
#define ff first
#define ss second
#define br cout<<"\n"
#define MOD (1000000007LL)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define eps (1e-6)
#define what_is(x) cerr << #x << " is " << x << "\n";
#define int long long int
#define infll 9e18
#define inf 1e12

#define lnode (2 * node + 1)
#define rnode (2 * node + 2)

using namespace std;

typedef pair<int, int> pii;

const int N = 3 * 1e6 + 2;

int n, k;

int32_t main(){

  FIO
  //cout << fixed << setprecision(10);
  //freopen("input.txt", "r", stdin);
  //freopen("output.txt", "w", stdout);

  cin >> k;
  int a, b;
  if(k == 1) return cout << "OK\n", 0;
  cin >> a >> b;
  if((a / k) * k >= a && (a / k) * k <= b) cout << "OK\n";
  else if((a / k) * k + k <= b) cout << "OK\n";
  else cout << "NG\n";


	return 0;
}




