#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define show(a) cout<<""#a""<<" is "<<a<<endl;
#define shw(a,b)cout<<"-->"<<a<<" "<<b<<endl;
#define print(arr,xx)for(int i=0;i<xx;i++)cout<<arr[i]<<" \n"[i>=xx];
#define here cout<<"here\n"; 
int caseno=0;
#define print_case cout<<"Case "<<++caseno<<": ";
#define fout freopen("output.txt","w",stdout);
#define fin freopen("input.txt","r",stdin);
#define pb push_back
#define ll long long
const int primemod=1e9+7;
#define fastio   
ll max(ll a,ll b) {return (a>b)?a:b;}
//string max(string a,string b) {return (a>b)?a:b;}
//ll min(ll a,ll b) {return (a<b)?a:b;}
const int maxsize = 100000+9;
void solve(){
	int a,b,k;
	cin>>k>>a>>b;
	bool ok =0;
	for(int i=a;i<=b;i++)if(i%k==0)ok=1;
	if(ok)cout<<"OK"<<endl;
	else cout<<"NG"<<endl;
}

int main(){
	#ifndef ONLINE_JUDGE
 	fout	
 	fin
 	int kase=1; 	
 	while(kase--){
 	#endif     
 	///-----		
 	//fastio
 	int T;
 	// cin>>T;
 	T=1;
 	while(T--){
 		 // if(solve())cout<<"Yes"<<endl;
 		 // else cout<<"No"<<endl;
 		solve();
 	}
 	///-----
 }
 
 #ifndef ONLINE_JUDGE
 }			
 #endif
