#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MOD = 1e9 + 7;
const int NMAX =1e5 + 10;

int main(int argc, char const *argv[])
{
	int k;
	int a,b;
	scanf("%d",&k);
	scanf("%d%d",&a,&b);
	if(a/k*k >= a && a/k*k <= b && b/k*k >= a && b/k*k <= b )
		puts("OK");
	else
		puts("NG");
	return 0;
}