#include <stdio.h>
#include <math.h>
#include <limits.h>
#include <string.h>
#include <stdlib.h>


#define scd(t) scanf("%d",&t)
#define scld(t) scanf("%ld",&t)
#define sclld(t) scanf("%lld",&t)
#define scc(t) scanf("%c",&t)
#define scs(t) scanf("%s",t)
#define scf(t) scanf("%f",&t)
#define prd(t) printf("%d",t)
#define prld(t) printf("%ld",t)
#define prlld(t) printf("%lld",t)
#define prc(t) printf("%c",t)
#define prs(t) printf("%s",t)
#define prf(t) printf("%f",t)
#define prsp() printf(" ")
#define prnl() printf("\n")
#define MOD 1000000007
#define MAX(a,b) a>b?a:b
#define MIN(a,b) a<b?a:b
#define fo(i,a,b) for(int i=a;i<b;i++)


void solve(){
	int k;
	scd(k);
	int a,b;
	scd(a); scd(b);
	int flag=1;
	/*for(int i=a;i<=b;i++){
		if(i%k==0){
			printf("OK");
			flag=0;
			break;
		}
	}*/
	int x=a/k;
	int y=(x+1)*k;
	if((y>a&&y<=b)||(x*k==a)) printf("OK");
	else  printf("NG");
}


int main(){
	#ifndef ONLINE_JUDGE
    // for getting input from input.txt
    freopen("input.txt", "r", stdin);
    // for writing output to output.txt
    freopen("output.txt", "w", stdout);
    #endif
	//int t; scd(t);
	//while(t--){
		solve();
		//prnl();
	//}
	return 0;
}