#include <bits/stdc++.h>
using namespace std;

#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define intll int long long
const int INF = 1e9;
const int MOD = 1e9 + 7;

int main() {
  int k , a , b ;
  cin >> k >> a >>  b ;
  bool ans = false ;
  
  rep(i,10000){
    int x = k ;
    x *= i ;
    if(x>= a && x<= b) ans = true;
  }
  
  if(ans) cout << "OK";
  else    cout << "NG" ;


}
