diff --git a/2020/day05/main.go b/2020/day05/main.go
index 306d92c..0da265e 100644
--- a/2020/day05/main.go
+++ b/2020/day05/main.go
@@ -15,27 +15,34 @@ func parseInput(file string) []string {
 	return strings.Split(string(content), "\n")
 }
 
+func calculateSeatID(pass string) int {
+	if len(pass) < 10 {
+		return -1
+	}
+	rowStr := pass[:7]
+	columnStr := pass[7:10]
+
+	row := 0
+	for idx, char := range rowStr {
+		if char == 'B' {
+			row |= 1 << (6 - idx)
+		}
+	}
+
+	column := 0
+	for idx, char := range columnStr {
+		if char == 'R' {
+			column |= 1 << (2 - idx)
+		}
+	}
+
+	return row*8 + column
+}
+
 func PartOne(input []string) int {
 	maxSeatID := 0
 	for _, pass := range input {
-		rowStr := pass[:7]
-		columnStr := pass[7:10]
-
-		row := 0
-		for idx, char := range rowStr {
-			if char == 'B' {
-				row |= 1 << (6 - idx)
-			}
-		}
-
-		column := 0
-		for idx, char := range columnStr {
-			if char == 'R' {
-				column |= 1 << (2 - idx)
-			}
-		}
-
-		seatID := row*8 + column
+		seatID := calculateSeatID(pass)
 		if seatID > maxSeatID {
 			maxSeatID = seatID
 		}