#include<stdio.h>
int main(){
  int k,a,b,i;
  scanf("%d",&k);
  scanf("%d %d",&a,&b);
  
  for(i=a;i<=b;i++){
    
   if(i%k==0){
    printf("OK\n"); 
     return 0;
   }
    
  }
  
  
  
  printf("NG\n");
 return 0; 
}