/* 
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
void hanoi(int N, int d)
  {
    if (N == 0) return;
    hanoi(N-1, -d);
    shift(N, d);    
    hanoi(N-1, -d);
  }