#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll N=1e5+5;
int main(){
    ios_base:: sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);
    ll k,a,b;cin>>k>>a>>b;
    for(ll i=a;i<=b;i++){
        if(i%k==0)return cout<<"OK" , 0;
    }
    cout<<"NG";
}
