///Astalavista Code........~CodeSlayer007
#include <bits/stdc++.h>
using namespace std;
#define endl "\n"
#define int long long
#define double long double
#define all(v) v.begin(),v.end()
#define allr(v) v.rbegin(),v.rend()
#define PT(x) cout << (#x) << " is " << (x) << endl;
#define SPD_emergency ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
const int M = 1e9 + 7;
int IM = 1e17;
void PV(vi v) { for (int i = 0 ; i < v.size() ; i++) cout << v[i] << " "; cout << endl;}
void PA(int v[], int n) {for (int i = 0 ; i < n ; i++)cout << v[i] << " " ; cout << endl;}
void IN(int a[], int n) {for (int i = 0; i < n; i++)cin >> a[i];}
inline void PTN(int n = 1, int a = 0, int b = 0, int c = 0) { if (n--)cout << a << " "; if (n--)cout << b << " "; if (n--)cout << c << " "; cout << endl; }
inline void open() {
#ifndef ONLINE_JUDGE
   freopen("input.txt", "r", stdin);
   freopen("output.txt", "w", stdout);
#endif
}
// <-------------------------------------------------------------------------------------------------------------------------------------------------------------------------> Ignore This-->  tuple first second push_back  continue make_pair break deque stack queue sort reverse accumulate  count lower_bound upper_bound next_permutation copy_n __builtin_popcount make_tuple
// <========================================================================================================================================================================

signed  main() {
   SPD_emergency

   //int t; cin >> t; int tt = 1; while (t--)
   {
      int k, a, b;
      cin >> k;
      cin >> a >> b;
      int n = b/k;
      n = n*k;     
      if( n>=a && n<=b)
         cout<<"OK";
      else
         cout<<"NG";
    
   }
   return 0;
}