#include<stdio.h>
#include <stdbool.h>
int main(){
   int k, a, b;
   bool judge = false;
   scanf("%d", &k);
   scanf("%d %d", &a, &b);
   
   for(int i=a; i<=b; i++){
      if(i % k == 0){
         judge = true;
      }
   }

   if(judge){
      printf("OK\n");
   } else {
      printf("NG\n");
   }

   return 0;
}
