/* 
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
int F(int i)
  { 
    if (i < 1) return 0;
    if (i == 1) return 1;
    return F(i-1) + F(i-2);
  }