#include<stdio.h>

int main(){
  int k,a,b,x,y;

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

  if(a % k == 0){
    x = a / k;
  }else{
    x = a / k + 1;
  }
  y = b / k;

  if(y - x >= 0){
    printf("OK\n");
  }else{
    printf("NG\n");
  }

  return 0;
}
