#include <bits/stdc++.h>
#define ff first
#define ss second
#define ll long long
#define rep(i, n) for (int i = 0; i < n; i++)
using namespace std;


int main() {

   ios::sync_with_stdio(false);   cin.tie(NULL);   cout.tie(NULL);

   int k, a, b;
   cin >> k >> a >> b;
   for (int i = a; i <= b; i++) {
      if (i % k == 0) {
         cout << "OK" << endl;
         return 0;
      }
   }
   cout << "NG" << endl;

   return 0;
}