#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <cmath>
#include <iomanip>

using namespace std;
using ll = long long;
using vi = vector<int>;

#define in(v) v; cin >> v;
#define all(f,c,...) (([&](decltype((c)) cccc) { return (f)(begin(cccc), end(cccc), ## __VA_ARGS__); })(c))
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return 1;}return 0;}

#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) for(int i=0,_i=(n);i<_i;++i)
#define repi(i,a,b) for(int i=(a),_i=(b);i<_i;++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)

// debug
template<class T>ostream& operator<<(ostream& os,const vector<T>& vec){os<<"{";for(size_t i=0;i<vec.size();++i)os<<(i?", ":"")<<vec[i];os<<"}";return os;}
ostream& operator<<(ostream& os,const vector<char>&v){for(size_t i=0;i<v.size();++i)os<<v[i];return os;}
template<class T1,class T2>ostream& operator<<(ostream& os,const pair<T1,T2>& rhs){os<<"("<<rhs.first<<", "<<rhs.second<<")";return os;}

#ifdef LOCAL
void debug() {cerr << "\n";}
template<class First> void debug(const First& first) {cerr<<first<<"\n";}
template<class First, class... Rest> void debug(const First& first, const Rest&... rest) {cerr<<first<<",";debug(rest...);}
void debug2() {cerr << "\n";}
template<class First> void debug2(const First& first) {cerr<<first<<" ";}
template<class First, class... Rest> void debug2(const First& first, const Rest&... rest) {cerr<<first<<" ";debug2(rest...);}
#else
#define debug(...) 42
#define debug2(...) 42
#endif

int main() {
  int in(K);
  int in(A);
  int in(B);

  rep(i, A, B+1) {
    if (i % K == 0) {
      cout << "OK\n";
      return 0;
    }
  }
      cout << "NG\n";

  return 0;
}
