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

int main(){
  int k,a,b;
  cin>>k>>a>>b;
  bool flag =false;
  for(int i=a;i<=b;i++){
    if (i%k==0) flag =true;
  }
  if (flag) cout <<"OK";
  else cout << "NG";
}
  