#include <stdio.h>

int main(){
  int K,A,B;
  scanf("%d %d %d",&K,&A,&B);
  
  if((B-A+1)>=K || A%K==0 || B%K==0){
    printf("OK\n");
  }else if(A%K>B%K){
    printf("OK\n");
  }else{
    printf("NG\n");
  }
  return 0;
}