

void main(){
	

	auto K = readLine!()()[0];
	auto AB = readLine!()();
	
	foreach( i ; 1..1000 ){
		if( AB[0] <= K*i  && K*i <= AB[1] ){
			writeln("OK");
			return;
		}
		if( K*i > 1001 ){break;}
	}
	writeln("NG");
	return;
}


import std.stdio, std.string, std.conv;
import std.math, std.algorithm, std.array;
import std.regex;

T[] readLine( T = size_t )( string sp = " " ){
	T[] ol;
	foreach( string elm ; readln().chomp().split(sp) ){
		ol ~= elm.to!T();
	}
	return ol;
}