diff --git a/gcany0n_fizzymagics_ineluctable_coin_puzzle/main.go b/gcany0n_fizzymagics_ineluctable_coin_puzzle/main.go
new file mode 100644
index 0000000..21ec1d8
--- /dev/null
+++ b/gcany0n_fizzymagics_ineluctable_coin_puzzle/main.go
@@ -0,0 +1,30 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/bitlux/caches/util"
+)
+
+const numbers = `19	23	30	 7	75	38	60	69	80
+ 6	74	28	37	19	 8	 5	26	 2
+ 5	32	 5	23	19	 2	 3	11	34
+ 8	68	64	29	29	23	13	22	 5
+22	61	22	98	16	25	96	 8	29
+17	23	29	48	 5	99	 4	16	32
+17	36	99	22	36	28	23	30	28
+ 2	61	32	18	 6	 5	25	23	38
+19	33	 8	22	69	26	32	 8	18`
+
+func main() {
+	for i, str := range strings.Fields(numbers) {
+		n, err := strconv.Atoi(str)
+		util.Must(err)
+		fmt.Printf("%c", util.A1Decode(util.CollatzStoppingTime(n)))
+		if (i+1)%9 == 0 {
+			fmt.Println()
+		}
+	}
+}
diff --git a/gcb41b3_analyze_this/main.go b/gcb41b3_analyze_this/main.go
index fa8d01c..26c64d5 100644
--- a/gcb41b3_analyze_this/main.go
+++ b/gcb41b3_analyze_this/main.go
@@ -30,7 +30,7 @@ If the implementation is easy to explain, it may be a good idea.
 Namespaces are one honking great idea -- let's do more of those!`
 
 func main() {
-	histo := util.Histogram(strings.ToLower(text))
+	histo := util.RuneCount(strings.ToLower(text))
 	fmt.Println(histo['m'] + histo['u'])
 	fmt.Println(histo['x'] + histo['y'])
 	fmt.Println(histo['x'] + histo['p'])
diff --git a/ipieces/ipieces.go b/ipieces/ipieces.go
index 9d0d957..80776f6 100644
--- a/ipieces/ipieces.go
+++ b/ipieces/ipieces.go
@@ -266,5 +266,5 @@ func (p Puzzle) Run() {
 		port = "8080"
 	}
 	fmt.Println("Listening on port", port)
-	log.Fatal(http.ListenAndServe(":8080", nil))
+	log.Fatal(http.ListenAndServe(":"+port, nil))
 }
diff --git a/util/file.go b/util/file.go
index 2287239..82697f0 100644
--- a/util/file.go
+++ b/util/file.go
@@ -10,6 +10,7 @@ const maxBuf = 1024 * 1024 * 1024 // 1 GiB
 func readLines(file string, size int) ([]string, error) {
 	f, err := os.Open(file)
 	Must(err)
+	defer f.Close()
 
 	buf := make([]byte, size)
 	scanner := bufio.NewScanner(f)
diff --git a/util/math.go b/util/math.go
index c6e6af7..a2af435 100644
--- a/util/math.go
+++ b/util/math.go
@@ -58,3 +58,19 @@ func FromDigitsBase[T constraints.Integer](digits []T, base int) int {
 func FromDigits[T constraints.Integer](digits []T) int {
 	return FromDigitsBase(digits, 10)
 }
+
+// CollatzStoppingTime returns the number of steps in the Collatz (3n+1) sequence before reaching 1.
+func CollatzStoppingTime(i int) int {
+	n := 0
+	for {
+		if i == 1 {
+			return n
+		}
+		if i%2 == 0 {
+			i /= 2
+		} else {
+			i = 3*i + 1
+		}
+		n++
+	}
+}
diff --git a/util/math_test.go b/util/math_test.go
index 4a8bb98..6ac4ca7 100644
--- a/util/math_test.go
+++ b/util/math_test.go
@@ -66,3 +66,17 @@ func TestFromDigits(t *testing.T) {
 		}
 	}
 }
+
+func TestCollatzStoppingTime(t *testing.T) {
+	for _, tc := range []struct {
+		input, want int
+	}{
+		{1, 0},
+		{19, 20},
+		{11, 14},
+	} {
+		if got := CollatzStoppingTime(tc.input); got != tc.want {
+			t.Errorf("CollatzStoppingTime(%d) = %d, want %d", tc.input, got, tc.want)
+		}
+	}
+}
diff --git a/util/text.go b/util/text.go
index 71fbef9..fa66f25 100644
--- a/util/text.go
+++ b/util/text.go
@@ -1,14 +1,5 @@
 package util
 
-// Histogram produces a count of all of the letters that appear in s.
-func Histogram(s string) map[rune]int {
-	histo := map[rune]int{}
-	for _, r := range s {
-		histo[r]++
-	}
-	return histo
-}
-
 // RuneCount returns a map containing each rune in s and how many times it occurs.
 func RuneCount(s string) map[rune]int {
 	ret := map[rune]int{}