diff --git a/internal/2017/DayFour/code.go b/internal/2017/DayFour/code.go
new file mode 100644
index 0000000..12ecbb9
--- /dev/null
+++ b/internal/2017/DayFour/code.go
@@ -0,0 +1,40 @@
+package dayfour
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"strings"
+)
+
+func init() {
+	registry.Register("2017D4", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	validCount := 0
+	for _, passphrase := range data {
+		words := strings.Fields(passphrase)
+		seen := make(map[string]bool, len(words))
+		hasDuplicate := false
+		for _, word := range words {
+			if seen[word] {
+				hasDuplicate = true
+				break
+			}
+			seen[word] = true
+		}
+		if !hasDuplicate {
+			validCount++
+		}
+	}
+	return validCount
+}
+
+func PartTwo(data []string) int {
+	return 0
+}