#include<bits/stdc++.h>
using namespace std;
int main()
{
    ios_base::sync_with_stdio(false),cin.tie(NULL),cout.tie(NULL);
    int k,a,b;
    cin>>k>>a>>b;
    if(b/k - (a-1)/k > 0)
    {
        cout<<"OK";
    }
    else
    {
        cout<<"NG";
    }
    
    return 0;
}