#include <stdio.h>

int main(){
  int k, a, b, i=1;
  scanf("%d", &k);
  scanf("%d %d", &a, &b);
  
  do {
    if ((a <= i*k) && (i*k <= b)){
      printf("OK\n");
      return 0;
    }
    i++;
  } while (i*k <= b);
    
  printf("NG\n");
  return 0;
}
