/*
 * Procedure:
 *   power
 * Parameters:
 *   base, an integer
 *   expt, an integer
 * Purpose:
 *   Computes base^expt
 * Produces:
 *   result, an integer
 * Preconditions:
 *   expt is non-negative
 * Postconditions:
 *   result = base^expt
 *   That is, result = base*base* ... * base, with expt copies of base.
 */
int power(int base, int expt);