#include<stdio.h>

int main(void) {

int a, b, k, i, count;
scanf("%d", &k);
scanf("%d", &a);
scanf("%d", &b);
count=0;

for (i=1; i < 1000; i++) {
   if (a<=(i*k)&&(i*k)<=b) {
count++;
  }
}
if (count==0) {
  printf("NG");
}
else{
  printf("OK");
}
  return 0;
}
