diff --git a/problems/LabOne_ChapterFive.h b/problems/LabOne_ChapterFive.h
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+//
+// Created by Ari Trachtenberg on 9/10/24.
+//
+
+// CHAPTER 5
+#include <string>
+using namespace std;
+
+/**
+ * @param nn A positive integer
+ * @return The sum of the following values:
+ *    a. The first digit of nn.
+ *    b. The last digit of nn.
+ *    c. The number of digits in nn.
+ *
+ *  @example
+ *  labOne_pFour(1729) returns 14, because:
+ *     a.  The first digit of 1729 = 1.
+ *     b.  The last digit of 1729 = 9.
+ *     c.  The number digits in 1729 = 4.
+ */
+int labOne_pFour(int nn);
+
+/**
+ * @param str Some string.
+ * @return The reverse of [str]
+ * @note Your function must be *recursive* in nature.
+ * @hint Reverse the substring starting at the second character,
+ *       then add the first character to the end.
+ *
+ * @example
+ * labOne_pFour("wolf") returns "flow".
+ */
+int labOne_pFive(string str);
+
+/**
+ * @param str Some string.
+ * @return true if and only if [str] is a palindrome
+ * @see https://en.wikipedia.org/wiki/Palindrome
+ *
+ * @example 1
+ * labOne_pSix("deed") == true because "deed" is the same forward as backward.
+ *
+ * @example 2
+ * labOne_pSix("deeds") == false because "deeds" backwards is "sdeed", and the
+ *     two strings are different.
+ *
+ * @example 3
+ * labOne_pSix("aibophpobia") == true because the string is the same forward as backward.
+ *
+ */
+bool labOne_pSix(string str);
+
+/**
+ * @param num A positive inteber <= 3628799.
+ * @return The number [num] in the factorial number system.
+ * @see https://en.wikipedia.org/wiki/Factorial
+ * @see https://en.wikipedia.org/wiki/Factorial_number_system
+ *
+ * @example 1
+ * labOne_pSix(3) = 11 because:
+ *    3 = 1*2! + 1*1!
+ *
+ * @example 2
+ * labOne_pSix(10) = 120 because:
+ *    10 = 1*3! + 2*2! + 0*1!
+ *
+ * @example 3
+ * labOne_pSix(463) returns 34101 because:
+ *    463 = 3*5! + 4*4! + 1*3! + 0*2! + 1*1!
+ */
+long labOne_pSeven(long num);
\ No newline at end of file
diff --git a/problems/LabOne_ChapterFour.h b/problems/LabOne_ChapterFour.h
new file mode 100644
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+++ b/problems/LabOne_ChapterFour.h
@@ -0,0 +1,94 @@
+//
+// Created by Ari Trachtenberg on 9/10/24.
+//
+
+// CHAPTER 4
+
+/**
+ * @input read in two positive integers, height and width
+ * @output a height x width rectangle of stars "*"
+ * @note You may use only *one* loop in your code - no
+ *       nested loops.
+ *
+ * @example 1
+ * height: 3
+ * width: 4
+ * ****
+ * ****
+ * ****
+ *
+ * @example 2
+ * height: 1
+ * width: 10
+ * **********
+ */
+void labOne_pZero();
+
+/**
+ * @input max The upper bound of sums
+ * @output The sum of the following terms:
+ *    a. The sum of the even integers between 2 and max (inclusive).
+ *    b. The sum of all square numbers between 1 and max (inclusive).
+ *    c. The sum of all positive powers of two less than or equal to max.
+ * @note: You must use *loops* to compute the component sums.
+ * @see https://en.wikipedia.org/wiki/Square_number
+ *
+ * @example 1
+ * Max: 2
+ * 5
+ *
+ * This is because 2+1+2 = 5:
+ *    a.  The sum of even integers between 2 and 2 inclusive (i.e., 2)
+ *    b.  The sum of all squares between 1 and 2 (inclusive) (i.e., 1)
+ *    c.  The sum of all positive powers of two less than or equal to 2 (i.e., 2)
+ *
+ * @example 2
+ * MaxL 9
+ * 47
+ *
+ * This is because 20+14+13 = 47:
+ *    a.  2+4+6+8 = 20
+ *    b.  1+4+9 = 14
+ *    c.  1+4+8 = 13
+ */
+void labOne_pOne();
+
+/**
+ * @input a string
+ * @output all substrings of the input, sorted by length.
+ *
+ * @example
+ * Input:  rum
+ * Output:
+ * r
+ * u
+ * m
+ * ru
+ * um
+ * rum
+ */
+void labOne_pTwo();
+
+/**
+ * @input an upper bound [u] for the numbers to consider
+ * @output A list of the numbers 2...[u] (inclusive) that
+ *    are *not* prime, one per line
+ *
+ * @example
+ * Input:  20
+ * Output:
+ * 4
+ * 6
+ * 8
+ * 9
+ * 10
+ * 12
+ * 14
+ * 15
+ * 16
+ * 18
+ * 20
+ *
+ */
+void labOne_pThree();
+