diff --git a/2020/day05.go b/2020/day05.go
index 3917a62..2fa82ee 100644
--- a/2020/day05.go
+++ b/2020/day05.go
@@ -42,5 +42,16 @@ func main() {
 		fmt.Println("Highest Seat Number:", max)
 	case "2":
 		// build a map of all seat numbers then just print the ones between 0 and 1024 that don't exist
+		seatMap := make(map[int]bool)
+		for _, line := range values {
+			seatNumber := calculateSeatNumber(line)
+			seatMap[seatNumber] = true
+		}
+
+		for i := 0; i < 1024; i++ {
+			if _, ok := seatMap[i]; !ok {
+				fmt.Println("Didn't find seat ", i)
+			}
+		}
 	}
 }