#include <stdio.h>
#include<stdlib.h>
#include<string.h>
#include <assert.h>

int main(void){
		int a,b,c,d;
    //int ans;
		scanf("%d",&a);
    scanf("%d",&b);
    scanf("%d",&c);

    d = c/a;
    //printf("%d\n",d);
    d = d*a;
    //printf("%d\n",d);

    //ans = c-d;

    //printf("%d\n",ans);

    if(b <= d && d <= c){
      puts("OK");
    }
    else{
      puts("NG");
    }


		return 0;
}
