diff --git a/index.php b/index.php
index c31e882..39ba95b 100644
--- a/index.php
+++ b/index.php
@@ -133,8 +133,8 @@
                     };
 
                     function draw(e) {
-                        var posX = (e.clientX - crect.left) * canvas.width / crect.width - 1;
-                        var posY = (e.clientY - crect.top) * canvas.height / crect.height - 1;
+                        var posX = ((e.clientX - crect.left) * canvas.width) / crect.width - 1;
+                        var posY = ((e.clientY - crect.top) * canvas.height) / crect.height - 1;
                         
                         ctx.putImageData(pen, posX, posY);
                     }