diff --git a/blocks.go b/blocks.go
index 8b3ba09..2c90f7a 100644
--- a/blocks.go
+++ b/blocks.go
@@ -1,5 +1,30 @@
 package defrag
 
+import (
+	"bytes"
+	"strconv"
+	"strings"
+)
+
 func Blocks(diskMap []byte) ([]byte, error) {
-	return nil, nil
+	current := 0
+	onFile := false
+	buff := bytes.Buffer{}
+	for _, by := range diskMap {
+		count, err := strconv.Atoi(string(by))
+		if err != nil {
+			return nil, err
+		}
+		onFile = !onFile
+		if count == 0 {
+			continue
+		}
+		append := "."
+		if onFile {
+			append = strconv.Itoa(current)
+			current++
+		}
+		buff.WriteString(strings.Repeat(append, count))
+	}
+	return buff.Bytes(), nil
 }
diff --git a/cmd/defrag/main.go b/cmd/defrag/main.go
index e620e91..99bdecf 100644
--- a/cmd/defrag/main.go
+++ b/cmd/defrag/main.go
@@ -1,10 +1,10 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"os"
-	"bytes"
 
 	"codeberg.org/danjones000/advent-of-code/2024-09/defrag"
 )