#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000000007;
const long long INF = 9999999999999999;
using ll = long long;
int main(){
  int K,A,B;
  cin>>K>>A>>B;
  if(A%K == 0 || B%K == 0){
    cout << "OK" << endl;
  }
  else{
    if(A/K != B/K){
      cout << "OK" << endl;
    }
    else{
      cout << "NG" << endl;
    }
  }
  return 0;
}