diff --git a/week5/app.py b/week5/app.py
index aac2c67..2aa9e81 100644
--- a/week5/app.py
+++ b/week5/app.py
@@ -6,7 +6,7 @@ from flask import render_template
 import glob
 import os
 
-UPLOAD_FOLDER = ".\static\img\\"
+UPLOAD_FOLDER = os.path.join("static", "img")
 ALLOWED_EXTENSIONS = {'txt', 'pdf', 'png', 'jpg', 'jpeg', 'gif'}
 def allowed_file(filename):
     return '.' in filename and \
@@ -36,11 +36,23 @@ from flask import request
 def upload_file():
     if request.method == 'POST':
         file = request.files['tile']
-        overwrite = request.form["overwrite"]
 
         if file and allowed_file(file.filename):
             filename, fileextension = os.path.splitext(file.filename)
-            file.save(os.path.join(app.config['UPLOAD_FOLDER'], (overwrite + fileextension) ))
+            overwrite = request.form["overwrite"]
+
+            input_file_path = os.path.join(app.config['UPLOAD_FOLDER'], (filename, fileextension))
+            overwritten_file_path = os.path.join(app.config['UPLOAD_FOLDER'], (overwrite, '.png'))
+
+            print("[input file path]:", input_file_path)
+            print("[overwritten file path]:", overwritten_file_path)
+
+            if 'png' not in fileextension:
+                print("--- convert uploaded image to png")
+                cmd = f"convert { input_file_path } { overwritten_file_path }"
+                os.system(cmd)
+                
+            file.save(overwritten_file_path)
         
         # print("==============================================================")
         # print(fileextension)