diff --git a/bin/deck b/bin/deck
index f43e49f..6f30566 100755
--- a/bin/deck
+++ b/bin/deck
@@ -11,6 +11,10 @@ var handlebars = require('handlebars');
 var app = express();
 var staticHandler = express['static'].bind(express);
 
+function toInt(num) {
+  return parseInt(num, 10);
+}
+
 app.use((function log() {
   var text = '{{date}} {{req.method}} {{req.url}}';
   var logTemplate = handlebars.compile(text);
@@ -50,17 +54,27 @@ function index(req, res) {
 
 app.get('/', index);
 
-app.get('/slides', function showHandler(req, res) {
+function getMarkdownFiles(cb) {
   fs.readdir(pathToFile('data', 'slide'), function (err, files) {
+    if (err) {
+      return cb(err);
+    }
     files.sort();
-    var jsonFiles = _.filter(files, function (file) {
+    var markdownFiles = _.filter(files, function (file) {
       return /^\d+\.md$/.test(file);
     });
+    cb(null, markdownFiles);
+  });
+}
+
+app.get('/slides', function showHandler(req, res) {
+  getMarkdownFiles(function (err, files) {
+    if (err) {
+      return renderError(res, err);
+    }
 
-    res.send(_.map(jsonFiles, function (file) {
-      return {
-        id: parseInt(file.replace(/\.md$/, ''), 10)
-      };
+    res.send(_.map(files, function (file, index) {
+      return {id: index + 1};
     }));
   });
 });
@@ -71,33 +85,23 @@ app.get(/slide\/(\d+)/, function showHandler(req, res, next) {
     return;
   }
 
-  var slideIndex = req.params[0];
+  var slideIndex = toInt(req.params[0]);
 
-  fs.readdir(pathToFile('data', 'slide'), function (err, files) {
+  getMarkdownFiles(function (err, files) {
     if (err) {
       return renderError(res, err);
     }
-
-    files.sort();
-    var markdownFiles = _.filter(files, function (file) {
-      return /\.md$/.test(file);
-    });
-
-    if (slideIndex > markdownFiles.length) {
+    if (slideIndex > files.length) {
       return next();
     }
 
-    var markdownFile = markdownFiles[slideIndex - 1];
+    var markdownFile = files[slideIndex - 1];
     var markdownPath = pathToFile('data', 'slide', markdownFile);
     fs.readFile(markdownPath, {encoding: 'utf8'}, function (err, content) {
       if (err) {
         return renderError(res, err);
       }
-
-      res.send({
-        id: parseInt(slideIndex, 10),
-        copy: content
-      });
+      res.send({id: toInt(slideIndex), copy: content});
     });
   });
 });
diff --git a/data/slide/01.md b/data/slide/010.md
similarity index 100%
rename from data/slide/01.md
rename to data/slide/010.md
diff --git a/data/slide/02.md b/data/slide/020.md
similarity index 100%
rename from data/slide/02.md
rename to data/slide/020.md
diff --git a/data/slide/03.md b/data/slide/030.md
similarity index 100%
rename from data/slide/03.md
rename to data/slide/030.md
diff --git a/data/slide/04.md b/data/slide/040.md
similarity index 100%
rename from data/slide/04.md
rename to data/slide/040.md
diff --git a/data/slide/05.md b/data/slide/050.md
similarity index 100%
rename from data/slide/05.md
rename to data/slide/050.md
diff --git a/data/slide/06.md b/data/slide/060.md
similarity index 100%
rename from data/slide/06.md
rename to data/slide/060.md
diff --git a/data/slide/07.md b/data/slide/070.md
similarity index 100%
rename from data/slide/07.md
rename to data/slide/070.md
diff --git a/data/slide/08.md b/data/slide/080.md
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rename from data/slide/08.md
rename to data/slide/080.md
diff --git a/data/slide/09.md b/data/slide/090.md
similarity index 100%
rename from data/slide/09.md
rename to data/slide/090.md
diff --git a/data/slide/10.md b/data/slide/100.md
similarity index 100%
rename from data/slide/10.md
rename to data/slide/100.md
diff --git a/data/slide/11.md b/data/slide/110.md
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rename from data/slide/11.md
rename to data/slide/110.md
diff --git a/data/slide/12.md b/data/slide/120.md
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rename from data/slide/12.md
rename to data/slide/120.md
diff --git a/data/slide/13.md b/data/slide/130.md
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rename from data/slide/13.md
rename to data/slide/130.md
diff --git a/data/slide/14.md b/data/slide/140.md
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rename from data/slide/14.md
rename to data/slide/140.md
diff --git a/data/slide/15.md b/data/slide/150.md
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rename from data/slide/15.md
rename to data/slide/150.md
diff --git a/data/slide/16.md b/data/slide/160.md
similarity index 100%
rename from data/slide/16.md
rename to data/slide/160.md
diff --git a/data/slide/17.md b/data/slide/170.md
similarity index 100%
rename from data/slide/17.md
rename to data/slide/170.md