```common lisp
(in-package #:euler)

(defun problem-1 ()
  (loop :for i :from 1 :below 1000
        :when (or (dividesp i 3)
                  (dividesp i 5))
        :sum i))

(defun problem-2 ()
  (loop :with p = 0
        :with n = 1
        :while (<= n 4000000)
        :when (evenp n) :sum n
        :do (psetf p n
                   n (+ p n))))

(defun problem-3 ()
  (apply #'max (prime-factorization 600851475143)))
```

Add comments with the Project Euler problem text
user
```common lisp
(in-package #:euler)

(defun problem-1 ()
  ;; If we list all the natural numbers below 10 that are multiples of 3 or 5,
  ;; we get 3, 5, 6 and 9. The sum of these multiples is 23.
  ;;
  ;; Find the sum of all the multiples of 3 or 5 below 1000.
  (loop :for i :from 1 :below 1000
        :when (or (dividesp i 3)
                  (dividesp i 5))
        :sum i))

(defun problem-2 ()
  ;; Each new term in the Fibonacci sequence is generated by adding the previous
  ;; two terms. By starting with 1 and 2, the first 10 terms will be:
  ;;
  ;;     1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
  ;;
  ;; By considering the terms in the Fibonacci sequence whose values do not
  ;; exceed four million, find the sum of the even-valued terms.
  (loop :with p = 0
        :with n = 1
        :while (<= n 4000000)
        :when (evenp n) :sum n
        :do (psetf p n
                   n (+ p n))))

(defun problem-3 ()
  ;; The prime factors of 13195 are 5, 7, 13 and 29.
  ;;
  ;; What is the largest prime factor of the number 600851475143 ?
  (apply #'max (prime-factorization 600851475143)))
```
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