#include<stdio.h>

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

   int judge = 0;
   if(1 <= a && a <= b && b <= 1000){
      for(int i=a; i<=b; i++){
         if(i % k == 0);
         judge = 1;
      }	

      if(judge == 1){
         printf("OK\n");
      } else {
         printf("NG\n");
      }	
   }
   printf("NG\n");

   return 0;
}
