#include<stdio.h>

int main(){
  int K,A,B;
  int c=0;
  
  scanf("%d\n%d %d",&K,&A,&B);
  for(int i=K;i<=B;i+=K){
    if(A<=i){
      c=1;
      break;
    }
  }
  if(c==0)
    printf("NG\n");
  else
    printf("OK\n");
  
  return 0;
}