#include <bits/stdc++.h>
using namespace std;
#define SPEED ios::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define fileio freopen("in.in", "r", stdin),freopen("out.out", "w", stdout);
#define ll long long int
#define FF first
#define SS second
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define pll pair<long long int,long long int>
#define sd(x) scanf("%d",&x)
#define slld(x) scanf("%lld",&x)
#define pd(x) printf("%d\n",x)
#define plld(x) printf("%lld\n",x)
#define pss printf
#define MOD 1000000007
#define INF 1e18
#define eps 0.00001
#define endl '\n'
#define debug(n1) cout<<n1<<endl
const int N = 1e5;  // limit for array size
ll n;  // array size

int main(){
       int k,a,b;cin>>k>>a>>b;
       for(int i=a;i<=b;i++){
       	if(i%k==0){
       		cout<<"OK"<<endl;return 0;
		   }
	   }
	   
	   cout<<"NG"<<endl;
	return 0;
}