#include <algorithm>
#include<iostream>
#include<vector>
#include<deque>
#include<queue>
#include<stack>
#include<list>
#include<map>
#include<set>
#include<string>
#include <sstream>

#include<stdlib.h>
#include<string.h>
#include<math.h>
#include<limits.h>
const int INF = 0x7fffffff;
using lll = long long;
using ull = unsigned long long;
using namespace std;


int main(){
  lll ii,jj,kk;
  vector<int> ret;
  int k,a,b;

  cin >> k >> a >> b;
  bool flg;
  flg = false;
  for(ii=a;ii<=b;ii++){
    if(ii % k == 0){
      flg = true;
    }
  }

  if(flg){
    cout << "OK" << endl;
  }
  else{
    cout << "NG" << endl;
  }
  return 0;
}
