#include <stdio.h>
 
int main(void){
  int K, A, B;

  printf("K A B = ");   
  scanf("%d %d %d",&K,&A,&B);  

  if(K==1)
       printf("ok \n");
   else if(A-B>=K)
       printf("ok \n");
   else
       printf("NG \n");

  return 0;
}