yao2030

(define (expmod base exp m)
  (cond ((= exp 0) 1)
	((even? exp)
	 (remainder (square (expmod base (/ exp 2) m)) m))
	(else (remainder (* base (expmod base (- exp 1) m)) m))))

(define (fermat-every n)
  (fermat-helper (- n 1) n))

(define (fermat-helper a n)

yao2030

(define (smallest-divisor n)
  (find-divisor n 2))
(define (find-divisor n test-divisor)
  (cond ((> (square test-divisor) n) n)
	((divides? test-divisor n) test-divisor)
	(else (find-divisor n (next test-divisor)))))

(define (divides? a b)
  (= 0 (remainder b a)))

yao2030

public class Binary
{
    public static void main(String[] args)
    {
	int N = Integer.parseInt(args[0]);
	int v = 1;
	while (v <= N/2)
	    v = v*2;
	int n = N;
	while (v > 0)

yao2030

(define (keep pred stuff)
	(cond 
	      ((word? stuff) 
	       (if (empty? stuff)
		   ""
		   (if (pred (first stuff))
		       (word (first stuff) (keep pred (bf stuff)))
		       (keep pred (bf stuff))))) 
	      (else
	        (if (empty? stuff) 

yao2030

(define (substrings wd)
	(if (empty? wd)
	(se "")
	(se (sub-helper wd) (substrings (bf wd)))))

(define (sub-helper wd)
	(if (= 1 (count wd))
            (se wd)
	(se wd (sub-helper (bl wd)))))

yao2030

(define (pal-helper wd)
	(cond ((<= (count wd) 1) #t)
              ((equal? (first wd) (last wd))
                 (and #t (pal-helper (bl (bf wd)))))
              (else #f)))


(define (palindrome? sent)
	(pal-helper (accumulate word sent)))

yao2030

 (define (roman-value letter)
	(cond ((equal? letter 'i) 1)
	      ((equal? letter 'v) 5)
              ((equal? letter 'x) 10)
              ((equal? letter 'l) 50)
              ((equal? letter 'c) 100)
              ((equal? letter 'd) 500)
              ((equal? letter 'm) 1000)
              (else 'huh?)))

yao2030

 (define (arabic sent)
	(if (= (count sent) 1)
            (roman-value (first sent))
            (if (< (roman-value (first sent)) (roman-value (first (bf sent))))
                   (+ (roman-value (first sent)) (- (first (bf sent))) (arabic (bf (bf sent))))
                   (+ (roman-value (first sent)) (arabic (bf sent))))))

yao2030

public class RelativePrime
{
    public static int max(int M, int N)
    {
	return M >= N ? M : N;
    }
    public static int min(int M, int N)
    {
	return M <= N ? M : N;
    }

yao2030

public class Binomial
{
    public static int[][] binomial(int N)
    {
	int[][] a = new int[N+1][N+1];

	for (int i = 1; i <= N; i++)
	    for (int j = 1; j <= i; j++)
		{
		    if (i == j)