#include <stdio.h>

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

 int largest = (b / k) * k;
 if (a <= largest) {
 	puts("OK");
 } 
   else {
 puts("NG");
}

 return 0;
 }
