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

int main(){
  int k;
  scanf("%d",&k);
  int a,b;
  scanf("%d%d",&a,&b);

  if(a/k!=b/k || a%k==0){
    printf("OK\n");}
  else{
    printf("NG\n");}
  
  return 0;
}
